Article locating and tracking apparatus and method

ABSTRACT

An activity based monitoring system is disclosed, the activity based monitoring system being configured to monitor a plurality of badges associated with a plurality of assets within a healthcare facility.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/141,457, filed May 8, 2002 which claims the benefit of U.S.Provisional Application Ser. No. 60/289,432, filed May 8, 2001; thisapplication further claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/462,216, filed Apr. 11, 2003, the disclosures ofthe above applications are hereby expressly incorporated by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention is related to monitoring activities and moreparticularly monitoring activities of persons and equipment in ahealthcare environment.

Caregivers such as nurses and other staff in a hospital ward, hospitalwing, or other healthcare facility generally work under high pressure,high stress and long hours. These caregivers should be highly responsiveto patient needs, in non-emergency as well as emergency situations. Dueto ever-increasing costs of healthcare and other economicpracticalities, efficient deployment of the caregivers in a healthcarefacility is desired, particularly at night when the number of caregiversis typically maintained at a minimum. Nevertheless, optimizingefficiency is of secondary importance relative to the primary objectiveof providing a high level of healthcare.

One approach to maximizing the efficiency of caregivers such as nursesin a hospital facility involves the use of a location and identificationsystem to continuously monitor the location of the caregivers. Forinstance, U.S. Pat. No. 4,275,385 to White, which is incorporated hereinby reference, discloses a personnel locating system where individuals tobe located wear transmitters, and each transmitter transmits a signalwhich corresponds to the identity of the wearer. This information isrelayed to and displayed at a central control unit. The information mayalso be displayed at remote terminals, used to control access toequipment or locations, or conveyed via a telephone interface to atelephone switching network to call the nearest telephone or to page thewearer of the transmitter. Additionally, newer communications systemsprovide even more than the relatively simple locating and telephoningfeatures disclosed in White. For example, U.S. Pat. No. 5,561,412 toNovak et al., U.S. Pat. No. 5,699,038 to Ulrich et al., and U.S. Pat.No. 5,838,223 to Gallant et al., all of which are incorporated herein byreference, disclose the use of communications systems that integrateseveral aspects of personnel and equipment locating, call/codeenunciation, and equipment status information.

As alluded to above, caregiver (e.g., nurse) to patient ratios continueto decline due to increasing economic pressures. Many healthcarefacilities are exploring ways to reduce the non-value added activitiesof the caregivers to maintain quality care while reducing the number ofcaregivers per patient. Computers hold promise for aiding the caregiversto work more efficiently by eliminating activities previously performedby caregivers and/or reducing the amount of time associated with theperformance of caregiver activities. However, conventional uses ofcomputers in the above locating and identification systems only supplythe caregivers with information and at the most alarms indicatingpossible adverse events. Computer systems need to become aware ofactivities within the hospital environment if they are to reduceemployee workload. To enable this evolution in computing technology,Activity Based Tracking (“ABT”) is needed. ABT is, in a general sense,the real-time connectivity of information (i.e., location, time, deviceactivity, etc.) to detect the occurrence of a specific activity forwhich a known response is acted upon by an automated system.

Generally speaking an ABT system performs better if the ABT systemincludes a locating and detection system with a relatively high locationresolution. In other words, the instances in which the ABT systemprovides value to the caregiver are increased if the ABT system is ableto determine the location of caregivers, patients, equipment, etc.(hereinafter, “assets”) with high resolution. Current tracking/locatingsystems used in hospitals are based on IR/RF in which the location ofthe fixed receiver determines the location of the tagged object.Utilizing this strategy, to increase the locating resolution (e.g., tomove from being able to determine which room a caregiver is in to beingable to determine that the caregiver is next to a patient's bed),additional receivers with limited range may be employed.

In one exemplary embodiment a system for tracking a plurality of movableassets in a healthcare environment is provided comprising a plurality ofbadges and a locating system. Each of the plurality of badges includinga transmitter, being adapted to be coupled to the asset, and beingconfigured to transmit an identification signal identifying the badge.The locating system being configured to receive the identificationsignal from the respective badge and to determine a location of theasset in the healthcare environment including a height associated withthe asset based at least in part on the identification signal. Thelocating system being further configured to determine if the height ofthe asset is an expected height.

In one exemplary method for monitoring an asset to determine if theasset has been dropped or has fallen, the method comprises the steps ofproviding a badge adapted to be coupled to the asset, the badge havingan accelerometer configured to monitor a vertical acceleration of theasset and a transmitter; monitoring the vertical component of theacceleration of the badge; transmitting information regarding thevertical acceleration of the badge; determining if the verticalacceleration of the badge has exceeded a threshold value; andidentifying the asset as having been dropped or as having fallen basedon the vertical acceleration exceeding the threshold value.

In another exemplary embodiment, a system for tracking a plurality ofmovable assets in a healthcare facility is provided. The systemcomprising a plurality of badges, a locating system, and at least oneportable device. Each of the plurality of badges including atransmitter, being adapted to be coupled to the asset, and beingconfigured to transmit an identification signal identifying the badge.The plurality of badges including a first badge being associated with afirst movable asset. The locating system being configured to receive theidentification signal from the first badge and to determine a locationof the first movable asset in the healthcare facility based at least inpart on the identification signal received from the first badge. The atleast one portable device including a controller, a display, a memory,an input device, and a transceiver. The portable device being configuredto generate a request signal to be received by the locating systemrequesting the location of the first movable asset in the healthcarefacility, to receive a location signal from the locating systemindicating the location of the first movable asset, and to provideappropriate directions to a first location in the healthcare facilitybased on the location of the first movable asset.

In yet another exemplary embodiment, a system for tracking a pluralityof movable assets in a healthcare facility is provided. The systemcomprises a plurality of badges, a locating system, and a virtualfacility interface. Each of the plurality of badges including atransmitter, being adapted to be coupled to the asset, and beingconfigured to transmit an identification signal identifying the badge.The plurality of badges including a first badge being associated with afirst movable asset. The locating system configured to receive theidentification signal from the first badge and to determine a locationof the first movable asset in the healthcare facility based at least inpart on the identification signal received from the first badge. Thevirtual facility interface including a display and an input device. Thevirtual facility interface presents a virtual facility including a mapof the facility and representations of various assets each having abadge associated therewith, the representations being positioned withinthe virtual facility based on the location information determined by thelocating system for each asset. At least the first asset includingmultiple representations including a first representation correspondingto a first status and a second representation corresponding to a secondstatus.

In still a further exemplary embodiment, a system for tracking aplurality of movable assets in a healthcare environment is provided. Thesystem comprising a plurality of badges and a locating system. Each ofthe plurality of badges including a transmitter and a displacementsensor, the badge being adapted to be coupled to the asset. The locatingsystem including a plurality of transmitters positioned at fixedlocations within the healthcare environment and a processor with anassociated receiver. The processor configured to receive anidentification signal from the respective badges. The plurality oftransmitters configured to transmit identification signals identifyingthe transmitter. A first badge is configured to receive the transmitteridentifying signals from the transmitters within range of the firstbadge, to transmit an identification signal to the processor of thelocating system, the identification signal including identificationinformation identifying the first badge and motion information collectedby the first badge based on the displacement sensor. One of theprocessor and the first badge determines the location of the first badgebased on the transmitter identifying signals received by the firstbadge.

In a further exemplary embodiment, a locating system is provided whereinthe location of a user is determined based in part on the position ofthe user within the field of view of a camera and the focal length ofthe camera when the user is in focus. In a still further exemplaryembodiment, a locating system is provided wherein a plurality of badgesare detected by one or more steerable transceivers which generate anexcitation signal of limited extent, the badges being configured torespond to the excitation signal.

Additional features and advantages of the present invention will beevident from the following description of the drawings and exemplaryembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary activity based tracking system thatincorporates various features of the present invention;

FIG. 2 illustrates an exemplary badge of the activity based trackingsystem shown in FIG. 1;

FIG. 3A illustrates typical movement of the badge shown in FIG. 2 when aobject tagged with the badge is in transit;

FIG. 3B illustrates typical movement in a vertical direction of thebadge shown in FIG. 2 when an object tagged with the badge is in transitand the object subsequently experiences a fall;

FIG. 4 illustrates an exemplary location method used by the activitybased tracking system of FIG. 1 to determine the location of taggedobjects based upon information received from the badges of the taggedobjects;

FIG. 5 illustrates an exemplary activity based tracking method used bythe activity based tracking system of FIG. 1 to perform activity basedtracking;

FIG. 6 illustrates an exemplary extubation prevention method which is aparticular embodiment of the activity based tracking method shown inFIG. 5;

FIG. 7 illustrates an exemplary fall prevention method which is aparticular embodiment of the activity based tracking method shown inFIG. 5;

FIG. 8 illustrates an exemplary modeling simulation method which is aparticular embodiment of the activity based tracking method shown inFIG. 5;

FIG. 9 illustrates an exemplary display generated by the activity basedtracking system of FIG. 1;

FIG. 10 illustrates a portable unit for use with the activity basedtracking system;

FIG. 11. illustrates an exemplary locating and tracking system of thepresent invention;

FIG. 12 illustrates the location of an asset in an area of interest;

FIG. 13A provides an illustration of one method of determining thelocation of an asset with the system of FIG. 11 in three dimensionalspace;

FIG. 13B provides an illustration of one method of determining thelocation of an asset with the system of FIG. 11 in two dimensionalspace;

FIG. 13C illustratively shows the effect of differing altitudes on thetwo dimensional location of FIG. 13B;

FIG. 14A illustrates an exemplary interaction between a transceiver anda badge of the exemplary locating and tracking system of FIG. 11;

FIG. 14B illustrates an exemplary interaction between a fixedtransmitter or pinger, a transceiver and a badge of the exemplarylocating and tracking system of FIG. 11;

FIG. 15 illustrates the interactions between a badge and multiple fixedpingers of the exemplary locating and tracking system of FIG. 11,wherein the badge determines its location based on signals from thefixed pingers;

FIG. 16 illustrates the interactions between a fixed receiver andmultiple fixed pingers of the exemplary locating and tracking system ofFIG. 11;

FIG. 17 illustrates another exemplary locating and tracking system ofthe present invention including at least one steerable antenna;

FIG. 18 illustrates that the at least one steerable antenna is steerablealong multiple directions;

FIG. 19 illustrates a method of locating an asset in two dimensionalspace and three dimensional space with the system of FIG. 17;

FIG. 20 illustrates a further exemplary locating and tracking system ofthe present invention including at least one camera;

FIG. 21 illustrates a method of locating an asset in two dimensionalspace and three dimensional space with the system of FIG. 20;

FIG. 22 illustrates yet another exemplary locating and tracking systemof the present invention; and

FIG. 23 illustrates exemplary zones of transmitters in the locating andtracking system of FIG. 22.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

While the invention is susceptible to various modifications andalternative forms, exemplary embodiments thereof have been shown by wayof example in the drawings and will herein be described in detail. Itshould be understood, however, that there is no intent to limit theinvention to the particular forms disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

FIG. 1 illustrates an exemplary activity based tracking (ABT) system 10which incorporates various features of the present invention therein. Ingeneral, the ABT system 10 is operable to monitor activities and causeexecution of actions in response to various activities. The exemplaryABT system 10 includes badges 12 used to tag persons 14 and equipmentsuch as beds 16 and ventilators 18. As further described below, badges12 may include passive RFID, active RF, active IR, or ultrasoundtransmitters, or other suitable transmitters configured to emit orgenerate an ID signal traveling in free space. The exemplary ABT system10 also includes short range absolute reference position (ARP) sensors20 operable to communicate with badges 12 and long range sensors 22operable to communicate with badges 12. As further described below,sensors 20, 22 may include passive RFID, active RF, active IR, orultrasound sensors, or other suitable sensors configured to receive anID signal traveling in free space. The exemplary ABT system 10 furtherincludes equipment sensors 24 operable to provide use and/or statusinformation associated with equipment such as beds 16, ventilators 18,and bed side rails 26. The exemplary ABT system 10 also includes videodisplays 28, an optional reference field generator 30, video cameras 32,and a master station 34.

The master station 34 is generally operable to receive information fromthe badges 12 and the equipment sensors 24, process the receivedinformation, and cause some action to be taken in response todetermining that the received information satisfies predefined criteriaor rules. The master station 34 includes memory 36, a processor 38, atransceiver 40, and software stored in the memory 36. The software whenexecuted by the processor 38 generally causes the master station 34 tomonitor persons 14 and equipment and cause certain actions to be takenin response to activities of the persons 14 and equipment. More detailsconcerning the types of activities monitored, the manner of monitoringthe activities, and the types of actions taken in response to themonitored activities are described below with reference to FIGS. 4–8.

As illustrated, the exemplary master station 34 is essentially acentralized computing system that executes software that causes themaster station 34 to implement appropriate logic for activity basedtracking. However, the master station 34 may alternatively beimplemented in a distributed manner with multiple computing systemsworking together to implement the logic. In particular, the masterstation 34 may be implemented with a server cluster or server farmcomprising several computing systems. Moreover, the master station 34may also incorporate computational power of hospital equipmentdistributed throughout the facility such as beds, monitoring devices,docking stations, etc. to distribute portions of the computationalburden associated with the logic to many processors.

The transceiver 40 of the master station 34 is coupled to the ARPsensors 20 and long range sensors 22 via a computer network or directwiring in order to receive and/or transmit information therebetween.Moreover, the transceiver 40 of an exemplary embodiment is also coupledto some of the equipment sensors 24 via a computer network or directwiring in order to receive and/or transmit information therebetween.Alternatively, the transceiver 40 includes wireless transmitters andreceivers in order to wirelessly communicate with some or all of the ARPsensors 20, long range sensors 22, and/or the equipment sensors 24.

The optional reference field generator 30 is generally operable toprovide a reference field from which the badges 12 generate headinginformation. As described below, the exemplary badges 12 includemagnetoresistive sensors that provide signals indicative of the sensors'orientation to a reference field such as Earth's magnetic field. Thereference field generator 30 is typically configured to generate astronger magnetic field than the Earth's magnetic field. As a result,the badges 12 used with the reference field generator 30 typicallyinclude a low cost magnetoresistive sensor that does not require tiltdetection or tilt correction.

The video displays 28 of the ABT system 10 are positioned at variouslocations throughout the facility (e.g., nurses' stations, hallways,utility rooms). The video displays 28 are operable to provide agraphical representation of the facility including the locations oftagged assets in the facility and the status of various equipment 15 inthe facility as illustrated in FIG. 9. Moreover, in an exemplaryembodiment, at least a portion of the video displays 28 are alsooperable to display representations of real-time streaming video. Thevideo displays 28 are implemented using various display technologiessuch as televisions, computer CRTs, liquid crystal displays (LCDs),light emitting diodes (LEDs), and display panels. In an exemplaryembodiment, handheld devices such as Palm™ Pilots, or Handspring™ Visorswhich are carried by the caregivers also include video displays 28.

The badges 12 are generally worn by or attached to assets, such aspersons 14 (e.g., doctors, nurses, interns, orderlies, visitors, etc.)or equipment to be monitored (e.g., beds 16, ventilators 18, IV pumps,etc). The badges 12 and the sensors 20, 22 generally each include areceiver, a transmitter, a combination transmitter and receiver, atransceiver, or other receiving or transmitting mechanisms suitable forcommunicating information between the badges 12 and the sensors 20, 22.In an exemplary embodiment, the badges 12 are operable to sendinformation such as a tag ID that uniquely identifies a given badge 12and/or displacement information indicative of motion and heading of thebadge to the sensors 20, 22. Moreover, the badges 12 of the exemplaryembodiment are further operable to receive information such as anacknowledgment from the sensors 20, 22.

The sensors 20, 22 of the exemplary ABT system 10 generally include areceiver operable to receive information transmitted by badges 12. Thesensors 20, 22 are also generally operable to forward the informationreceived to the master station 34 and/or provide the master station 34with a sensor ID that uniquely identifies the sensor 20, 22. The sensorID enables the master station 34 to track the location of each taggedasset (i.e., person 14 or equipment) based upon which sensors 20, 22received information from the badges 12 of tagged assets as the taggedassets move through the facility.

According to one embodiment of the invention, a person 14 may enter afloor of a hospital wearing a badge 12. The system recognizes thatperson 14 has entered the floor when person 14 moves within range of ARPsensor 20, whereupon the passive RFID transceiver of badge 12 isactivated and transmits an ID associated with badge 12 (and person 14).The ID is received by a sensor 20 including an RFID interrogator locatedat a doorway entrance to the floor. As further explained herein, thenetwork establishes an initial location point for person 14 by knowingthe specific location of the RFID interrogator. The RFID interrogatormay also be configured to transmit, for example, patient assignments toperson 14, which are received by badge 12 and stored in badge memory 36.The system may then detect person 14 in a hallway of the floor with asensor 22 including an active RF sensor for detecting ID signalstransmitted by badge 12 with an active RF transmitter that periodicallytransmits the ID signal (e.g., every 5 seconds). As person 14 enters apatient room, the system may detect three signals from person 14 (i.e.,an active RF signal indicating that person 14 is on the floor, an activeIR signal indicating that person 14 is in a specific patient room, and apassive RFID signal indicating that person 14 is in the door entryway tothe specific patient room). By installing RFID interrogators atdifferent locations within such patient rooms, the system may accomplishincreased resolution regarding the location of person 14 within theroom.

In an exemplary embodiment, each badge 12 includes a passive RFtransmitter which is fully or partially powered by an ARP sensor 20 whenin close proximity to the ARP sensor 20 (e.g., within 3 feet). Inresponse to being in close proximity to the ARP sensor 20, the passiveRF transmitter of the exemplary badges 12 transmits the identificationsignal to the ARP sensors 20. For example, the RF transmitter of a badge12 transmits the identification signal to an RF receiver of an ARPsensor 20 in the doorway of patient room A when the badge 12 passesthrough the doorway of the patient room A. The ARP sensor 20 thenprovides information identifying the particular badge 12 to the masterstation 34 and information identifying the particular ARP sensor 20 forfurther processing and recording. In an exemplary embodiment, the ARPsensor 20 includes an RF identification receiver or a limited focus IRreceiver. In general, the ARP sensor 20 enables the master station 34 toestablish a very specific location of a badge 12. More specifically, theARP sensors 20 are used by the master station 34 to re-calibrate thelocation of the badges 12 as they pass within close proximity of the ARPsensors 20.

In one embodiment of the ABT system 10, visitors and patients are alsoprovided with badges 12 to enable the master station 34 to monitor theirmovements through the facility. In such an embodiment, visitors andpatients are given active badges which actively transmit anidentification signal. In an alternative embodiment, visitors andpatients are given passive badges which transmit an identificationsignal when in close proximity to one of the ARP sensors 20 locatedthroughout the facility.

The badges 12 may also be attached to equipment (e.g., IV pumps, beds16, ventilators 18, carts, diagnostic equipment, or the like) to bemonitored by the ABT system 10 and generally enable the location ofequipment to be tracked throughout the facility. As a result ofproviding the ABT system 10 with information concerning the location ofequipment, the ABT system 10 causes actions to be executed based uponthe location of the equipment and/or persons' interactions with suchequipment.

The equipment sensors 24 are generally associated with equipment andgenerally enable the ABT system 10 to monitor the use and/or status ofsuch equipment. For example, equipment sensors 24 are attached to theelectrical plugs of the equipment to determine whether the equipment isdrawing a current. In an exemplary embodiment, the badges 12 that areattached to certain equipment further include equipment sensors 24. Theequipment sensors 24 enable the ABT system 10 to cause actions to beexecuted based upon use and/or status of the equipment. Furthermore, byreporting when the equipment is activated and de-activated, theequipment sensors 24 enable the hospital to charge patients for theactual amount of time the equipment was used instead of utilizingnational averages based on the type of illness of the patient.

In an exemplary embodiment, the badges 12 and the sensors 20, 22 furtherinclude anti-collision technology that allows for information to betransferred between a single sensor 20, 22 and multiple badges 12 in asimultaneous or pseudo-simultaneous (e.g., TDMA, CDMA) manner. Use ofanti-collision technology allows for several badges 12 to be detected atthe same time by the same sensor 20, 22 thereby providing the ABT system10 with the ability to identify persons 14 and equipment in closeproximity to one another and accurately track their respective locationsand activities.

Additional details concerning the structure and function of a suitablesystem for locating and tracking persons 14 and to support various otherfeatures of the present invention are disclosed in U.S. Pat. No.5,561,412, the disclosure of which is hereby incorporated by reference.Other location and tracking systems are disclosed in U.S. Pat. No.6,344,794 filed Jan. 7, 2000, and U.S. patent application Ser. No.09/699,796, filed Oct. 30, 2000, now U.S. Pat. No. 6,727,818 thedisclosures of which are hereby incorporated by reference. Additionallocation and tracking systems are disclosed in U.S. Pat. Nos. 4,275,385;4,601,064; Re 35,035; 5,633,742; 5,745,272; 5,818,617; 5,119,104;5,387,993; 5,548,637; 5,572,195; 5,291,399; 5,455,851; 5,465,082;5,515,426; 5,594,786; 5,689,229; 5,822,418; 5,822,544; 5,699,038 and5,838,223.

In an exemplary embodiment, the badges 12 are implemented in a mannersimilar to the badges described in U.S. Pat. Nos. 5,561,412, 6,344,794,and co-pending U.S. patent application Ser. No. 09/699,796 in which thelocation of a badge 12 is determined solely upon which sensors of thelocation and tracking system detect the badge 12.

Alternatively, the badges 12 include components which aid in trackingthe location of the badges 12 and thus enable a reduction in the numberof sensors otherwise required to track the location of the badges 12 ina high resolution manner. As depicted in FIG. 2, the exemplary badges 12include a displacement sensor 50, a controller 52, a transmitter 54, areceiver 56, and a memory 58. The displacement sensor 50 is configuredto generate one or more signals the combination of which is indicativeof a motion and a heading of a “tagged asset.” As indicated above,tagged assets may include persons (e.g., doctors, nurses, orderlies,visitors, etc.), and equipment (e.g., a hospital bed 16, IV pumps,ventilators 18, heart monitors, medication containers, charts, portabletelevisions, etc.), or any other tangible thing desired to be locatedand/or tracked.

As depicted, the displacement sensor 50 generally comprises a motionsensor 60 and a direction sensor 62. The motion sensor 60 is generallyoperable to sense movement of the tagged object and generate one or moresignals that in combination are indicative of the sensed movement. Themotion sensor 60 includes a mono-axis, dual-axis, or tri-axisaccelerometer which generates one or more signals that in combinationare indicative of the dynamic acceleration (e.g., vibration inducedacceleration) and/or static acceleration (e.g., gravity inducedacceleration) of the tagged asset. In particular, the motion sensor 60of the exemplary embodiment includes an ADXL202 accelerometer fromAnalog Devices which is a low cost, low power, complete two-axisaccelerometer with a measurement range of ±2 g. The ADXL202accelerometer measures both dynamic acceleration (e.g., vibration) andstatic acceleration (e.g., gravity) and generates a first Duty CycleModulated (“DCM”) signal whose duty cycle (ratio of pulsewidth toperiod) is proportional to the acceleration in a first sensitive axis(e.g., x-axis) and a second DCM signal whose duty cycle is proportionalto acceleration in a second sensitive axis (e.g., y-axis).

The following Analog Devices publications further describe the ADXL202accelerometer and methods for relating the sensed accelerations todistances traveled: “ADXL202/ADXL201—Low cost ±2 g/±10 g Dual AxisiMEMS® Accelerometers with Digital Output” (Datasheet, Rev. B-4/99) and“Using the ADXL202 in Pedometer and Personal Navigation Applications,”by Harvey Weinberg, the disclosures of which are hereby incorporatedherein by reference.

The direction sensor 62 of the displacement sensor 50 is generallyoperable to generate one or more signals that in combination areindicative of the directional orientation or heading of the badge 12with respect to a reference direction and therefore indicative of thedirection traveled by the asset tagged with the badge 12. The directionsensor 62 of the exemplary embodiment includes a two-dimensionalmagnetoresistive field sensor such as the Philips KMZ52 sensor or twoone-dimensional magnetoresistive field sensors such as the Philips KMZ51which generate one or more signals indicative of the horizontalorientation of the badge 12 with respect to a reference direction suchas magnetic north, true north, or some other direction defined by anassociated reference field such as the Earth's magnetic field or anartificially generated field such as that generated by reference fieldgenerator 30. The exemplary direction sensor 38 further includes supportelectronics such as a flip coil driver and pre-amps which are used tocalibrate the field sensors and interface the field sensors with thecontroller 32 as explained in Philips Semiconductor publication“Electronic Compass Design using KMZ51 and KMZ52, Application NoteAN00022”, dated Mar. 30, 2000.

As indicated above, the exemplary ABT system 10 includes a referencefield generator 30 that enables the badge 12 to be implemented withouttilt correction. However, in an alternative exemplary embodiment, thedirection sensor 62 further includes mechanical or electrical gimbalingcomponents that maintain the two sensitive axes of the field sensor in ahorizontal plane (e.g., maintain an x-axis and a y-axis perpendicularwith Earth's gravity). To support electronic gimbaling or tiltcompensation, the direction sensor 62 includes a three-dimensional fieldsensor and a pitch-and-roll sensor. The three-dimensional field sensorincludes three sensitive orthogonal axis sensors that generate one ormore signals which in combination are indicative of a three-dimensionalspatial orientation of the badge 12 with respect to a reference fieldsuch as Earth's magnetic field or a generated field such as thatgenerated by the reference field generator 30. Further, thepitch-and-roll sensor generates one or more signals indicative of theorientation of the field sensor with respect to gravity. In particular,the pitch-and-roll sensor includes a two-dimensional accelerometer, suchas the ADXL202 accelerometer described above, including two orthogonalaxis sensors that generate one or more signals. These signals, incombination, are indicative of the static acceleration experienced bythe badges 12 due to gravity.

The transmitter 54 of the badges 12 is coupled to the controller 32 toreceive one or more signals indicative of information to be transmitted.Similarly, the receiver 56 is coupled to the controller 52 to providethe controller 52 with one or more signals indicative of informationreceived. The transmitter 54 and the receiver 56 include infrared (IR),radio frequency (RF), and/or other wireless transmission and receptioncomponents which utilize one or more different transmission protocols.More specifically, as indicated above, the transmitter 52 includes apassive RF transmitter to transmit identification information such as atag ID to the ARP sensors 20. Passive RF transmitters i) do not requirebattery power to transmit information, and ii) generally must pass closeto an ARP sensor 20 in order to transmit information which insures ahigh resolution point for the absolute position.

The controller 52 in general controls the transmission and reception ofinformation to and from the badges 12. In an exemplary embodiment, thecontroller 52 is implemented with a low cost microcontroller such as theMicroChip PIC16C54. Besides controlling the transmission and receptionof information to and from the badges 12, the controller 52 alsoprocesses the displacement signals received from the displacement sensor50 and stores displacement samples in the memory 58 that arerepresentative of the motion and heading of the badges 12 as sensed bythe displacement sensor 50. In particular, the controller 52 in anexemplary embodiment processes one or more motion signals from thedisplacement sensor 50 to obtain motion data that is indicative of thespeed of the badge 12 and heading data indicative of the heading of thebadge 12.

FIG. 3A shows waveforms representing an exemplary vertical acceleration,“A_(y),” and an exemplary horizontal acceleration, “A_(x),” of a personwalking or running. In general, pedestrian travel is fairly rhythmicpursuant to the gait of the pedestrian. Accordingly, as the person walksor runs through the facility, the badge 12 attached to the person isaccelerated vertically and horizontally in a generally periodic manner.Each step or stride taken by the person is detectable as the period ofA_(y). Thus, the frequency of A_(y) is proportional to the number ofsteps taken by the caregiver per unit of time, which is proportional tothe approximate pace at which the person walks or runs.

In the exemplary embodiment discussed above in connection with FIG. 2,the controller 52 receives one or more signals from the displacementsensor 50 that are indicative of the vertical acceleration A_(y). In theexemplary embodiment, the controller 52 determines the approximate speedof movement of the person by processing the received signals to obtainthe frequency of the vertical acceleration A_(y) which is indicative ofthe speed of the person.

In the case of wheeled objects or objects on skids (e.g., hospital beds16, carts, tables, etc.) the accelerations imparted to the tag or badge12 attached to the object are fairly periodic in nature due to eachrevolution of the wheel(s) or vibrations of the skid(s). In an exemplaryembodiment, a ridge or a bump is added to a wheel of a wheeled object inorder to aid in the generation of a discernable amount of acceleration.In any event, although the relationship of the vertical accelerationA_(y), horizontal acceleration A_(x), and time may vary betweendifferent types of assets, and even between different pedestrians, thefairly periodic nature of the accelerations imparted to the badges 12while the object is in motion are readily discemable via the appropriatesignal processing algorithms. Moreover, the displacement sensor 50 maygenerate the signals based on other parameters that vary with the speedof movement of the object. For example, the displacement sensor 50 forwheeled assets may include a more conventional type speedometer thatsenses the rotation of the wheels and generates signals based upon thesensed rotation of the wheels.

In an exemplary embodiment, discussed above in connection with FIG. 2,controller 52 of badge 12 receives one or more signals from thedisplacement sensor 50 that are indicative of the vertical acceleration(A_(y)) of badge 12. Controller 52 monitors the vertical acceleration(A_(y)) to determine the speed of badge 12, as discussed above inconnection with FIG. 3A, and to determine if the asset (person orequipment) associated with badge 12 has fallen or has been dropped.Assuming an asset associated with badge 12 falls or is dropped, thevertical acceleration (A_(y)) of badge 12 will exhibit a substantialchange in the magnitude of the vertical acceleration (A_(y)) asillustrated in FIG. 3B. In one example, badge 12 includes athree-dimensional accelerometer and acceleration data in all threedirections is monitored for substantial changes in magnitude.

Turning to FIG. 3B, the vertical acceleration (A_(y)) of a patientwalking and subsequently falling is shown. A first portion 70 of thecurve associated with vertical acceleration (A_(y)) exhibits therhythmic pattern discussed above in connection with FIG. 3A indicativeof a person walking. The first portion is followed by a second portion72 corresponding to a substantial change in the magnitude of verticalacceleration (A_(y)) indicative of a fall. Assuming the patient is atleast partially immobilized due to the fall, the vertical acceleration(A_(y)) associated with badge 12 will generally return to a baselinevalue as indicated by third portion 74. In one example, the verticalacceleration (A_(y)) in second portion 72 is indicative of a fall ordrop if the vertical acceleration (A_(y)) exceeds a threshold amount 76.Threshold amount 76 in one example is the same for all assets. Inanother example, threshold amount 76 is different for at least one typeof asset. Further, in an additional example, a characteristic of anasset is used in determining the threshold amount 76.

The vertical acceleration (A_(y)) data generated by badge 12, in oneexample, is processed by badge 12 to determine the speed of the assetassociated with badge 12 and to determine if the asset associated withbadge 12 has fallen or been dropped. In another example, the verticalacceleration (A_(y)) data is forwarded to master station 34 whichprocesses the vertical acceleration (A_(y)) to determine the speed ofthe asset associated with badge 12 and to determine if the assetassociated with badge 12 has fallen or been dropped.

In an exemplary embodiment, the master station 34 receives thedisplacement samples from the badges 12 and further processes thedisplacement samples to obtain an estimated distance traveled and anestimated heading traveled. In particular, the master station 34determines the estimated distance traveled based upon the motion datareceived from the badges 12 in a manner similar to one of the methodsdescribed in “Using the ADXL202 in Pedometer and Personal NavigationApplications,” by Harvey Weinberg. The master station 34 also determinesan estimated heading traveled from the motion data and/or the headingdata received from the badges 12. In particular, the master station 34performs one or more of the following functions on the motion dataand/or the heading data: offset-elimination, temperature driftcompensation, non-orthogonality correction of sensor axes, interferencefield correction, declination compensation, tilt compensation, and truenorth compensation in a manner similar to those described in “ElectronicCompass Design Using KMZ51 and KMZ52.” Alternatively, the controller 52of the badges 12 may be implemented with a more powerful processor whichexecutes software or firmware instructions to implement all or portionsof the functions performed on motion data and/or heading data describedabove.

Shown in FIG. 4 is a location tracking method 100 used to track thelocation of objects tagged with badges 12. In step 102, the badge 12determines whether the badge 12 is within the limited range of an ARPsensor 20. If the badge 12 is within range of the ARP sensor 20, thenthe badge 12 in step 104 transmits a tag ID to the ARP sensor 20 thatuniquely identifies the badge 12. More specifically, the badge 12includes a passive RF transmitter that is powered by the ARP sensors 20when in range of the ARP sensors 20. Accordingly, the badge 12determines that the badge 12 is within range of the ARP sensor 20 if thetransmitter 54 of the badge 12 is powered by the ARP sensor 20. In step104, the ARP sensor 20 that receives the information from the badge 12provides the master station 34 with the tag ID received from the badge12 and a sensor ID that identifies the ARP sensor 20.

In a power saving embodiment of the badge 12, the ARP sensor 20 in step104 further causes the badge 12 to power active portions of the badge 12(e.g., displacement sensor 50, controller 52) with an on-board battery(not shown). In particular, after receiving power from the ARP sensor 20and initiating battery operation of the active portions, the badge 12continues to power the active portions until the controller 52 detects apower off condition. For example, the controller 52 may remove batterypower from the active portions of the badge 12 after determining thatthe badge 12 has not received transmissions from the sensors 20, 22 fora predetermined time period (e.g., 10 minutes), and/or that the badge 12has been static (i.e., substantially still) for a predetermined timeperiod (e.g., 5 minutes).

In step 106, the master station 34 determines the location of the badge12 and associated tagged object from the tag ID and the sensor ID. Morespecifically, the master station 34 includes facility map informationthat defines the location of doorways, walls, ARP sensors 20, and otherstatic features of the facility. From the facility map information andthe information received from the ARP sensor 20 in step 104, the masterstation 34 determines that the current location of the tagged object isthe ARP sensor 20 identified by the received sensor ID.

The badge 12 in step 108 starts transmitting displacement samples at apredetermined interval (e.g., every 5 seconds). In an exemplaryembodiment, the badge 12 transmits signals representative of the tag IDand all displacement samples that have been stored in the memory 58since receiving an acknowledgment of a prior displacement sampletransmission. In an exemplary embodiment, the controller 52 obtainsdisplacement samples from the displacement signals of the displacementsensor 50 on a predetermined interval (e.g., 1 millisecond intervals)and stores the obtained displacement samples in the memory 58. Inparticular, the controller 52 periodically samples the receiveddisplacement signals during the given interval to obtain displacementsamples that are generally representative of the displacement signalsduring the interval. After obtaining the displacement samples for theinterval, the controller 52 stores the displacement samples in thememory 58. In an alternative embodiment, the badge 12 transmits thedisplacement samples at various different intervals depending upon therate of movement of the badge 12 as described in U.S. Provisional PatentApplication 60/306,818, filed Jul. 20, 2001, converted to U.S. patentapplication Ser. No. 10/199,849, now U.S. Pat. No. 6,972,683 andentitled “Locating Badge with Intelligent Transmission Based onAcceleration,” the disclosure of which is hereby incorporated byreference.

In an alternative embodiment, the controller 52 combines displacementsamples to reduce the number of displacement samples stored in thememory 58. In particular, the controller 52 combines displacementsamples that are temporally adjacent to one another and that do notsignificantly differ from one another. For example, if the controller 52determines that the motion and heading of temporally adjacentdisplacement samples are within a predetermined tolerance, then thecontroller 52 combines the two displacement samples (e.g., averaging thesamples, discarding one of the samples) to obtain a displacement samplerepresentative of the interval associated with both displacementsamples. In this manner, the controller 52 obtains a single displacementsample that is representative of several temporally adjacentdisplacement samples thus reducing the number of samples stored in thememory 58.

Further, the controller 52 of the alternative embodiment includes timinginformation with the displacement samples. For example, the controller52 includes a count value with the motion data and heading data of thedisplacement samples to indicate the number of samples of which thestored displacement sample is representative. Alternatively, thecontroller 52 includes a timestamp value with the displacement samples.The controller 52 may instead utilize other techniques for correlatingthe motion data and heading data of a displacement sample to arespective time interval such as including an interval sequence countwith the displacement samples.

As a result of periodically transmitting the displacement samples andtag ID in step 112, receivers of the sensors 22 in step 114 receivesignals that are representative of the displacement samples and tag IDof the badge 12. The sensors 22 further provide the master station 34with information representative of the tag ID and displacement samplesin step 114.

The master station 34 in step 116 determines the movement path andlocation of the badge 12 based upon the received tag ID, displacementsamples, and the previously determined location for the badge 12 (e.g.,location of an ARP sensor 20, or location determined from displacementsamples). The master station 34 processes the motion data, heading data,and optionally the timing data of the displacement samples to determinethe movement path of the badge 12. Techniques for obtaining distanceinformation from motion data are described in the previously referencedAnalog Devices publications.

The master station 34 in step 116 further adjusts the movement path andlocation to prevent a conflict between the calculated movement path forthe badges 12 and the layout information for the facility. For example,the calculated movement path may indicate that the tagged object passedthrough a wall at a location near a doorway and then proceeded down ahallway outside the doorway. The master station 34 may alter thecalculated movement path to indicate the reality that the tagged objectpassed through the doorway. Methods such as fuzzy logic, neuralnetworks, expert systems, and/or other artificial intelligencetechniques for correlating location information with map information areknown.

In response to receiving the tag ID and displacement samples from thebadges 12, the master station 34 in step 118 causes an acknowledgment tobe sent to the badge 12 via a transmitter such as the RF and/or IRtransmitters of the ARP sensors 20 or the long range sensors 22. If thebadge 12 receives the acknowledgment, then the controller 52 in step 120reclaims the storage area of the memory 58 used to store theacknowledged displacement samples. However, if the controller 52determines in step 120 that the badge 12 did not receive theacknowledgment message within a predefined timeout period (e.g., 1second), then the controller 52 returns to step 112 in order toretransmit the tag ID and displacement samples.

In one embodiment, badge 12 is configured to transmit the displacementsamples and tag ID at two or more transmission rates to reduce errors inthe calculated location of badge 12 due to rapid changes in direction.It is possible that errors in location of badge 12 can arise due to thechanges in direction of badge 12 between two transmissions of badge 12.For example, assume that the transmission rate of badge 12 is once persecond and at a first time (t=1 second), the last known location ofbadge 12 is ten feet north of ARP sensor 20 and badge 12 transmits asignal including displacement information indicating that badge 12 ismoving north of ARP sensor 20 at a speed of 2 feet per second.Immediately after transmitting the displacement information at the firsttime, badge 12 changed direction and began heading back towards ARPsensor 20 at two feet per second. At a second time (t=2 seconds), badge12 sends a second transmission including displacement informationindicating that badge 12 is moving south toward ARP sensor 20 at a speedof 2 feet per second.

As such the true location of badge 12 at the second time is generallyeight feet north of ARP sensor 20. However, master station 34 assumesthat badge 12 is moving north at two feet per second between the firsttime an the second time. As such, master station 34 will incorrectlycalculate the location of badge 12 to be twelve feet north of ARP sensor20 and heading south toward ARP sensor 20 at two feet per second. Inorder to reduce or generally eliminate this discrepancy in the locationof badge 12, badge 12 is configured increase its associated transmissionrate in response to rapid changes in direction of badge 12. In oneexample, whenever there is a rapid change in direction of badge 12,badge 12 immediately generates a transmission including the newdisplacement information. In another example, whenever there is a rapidchange in direction, badge 12 increases the transmission rate of badge12 for a preset time period. For example, badge 12 in the above examplemay begin transmitting at a rate of four times a second for the nextthree seconds.

Referring now to FIG. 5, there is depicted an activity based trackingmethod 150 implemented by the ABT system 10. The master station 34 ofthe ABT system 10 in step 152 receives information from the ARP sensors20 that is indicative of the location of tagged objects associated withthe badges 12. The master station 34 in step 154 processes theinformation received in step 152 and updates location information forthe tagged objects associated with the badges 12 accordingly.

The master station 34 also receives in step 156 information from theequipment sensors 24 that is indicative of the use/status of theequipment associated with the equipment sensors 24. In step 158, themaster station 34 processes the information received in step 156 andupdates use/status information for the equipment associated with theequipment sensors 24.

The master station 34 in step 160 analyzes the updated location anduse/status information to determine whether actions need to be taken inresponse to the received information. In particular, the master station34 determines for each predefined rule whether all conditions associatedwith the rule have been satisfied. If the updated location and/oruse/status information satisfies the conditions of a given rule, thenthe master station 34 in step 162 causes actions associated with eachsatisfied rule to be executed. However, if the master station 34determines that no predefined rule has been satisfied, then the masterstation 34 returns to step 62 in order to process additional informationfrom the ARP sensors 20 and the equipment sensors 24.

Hygiene monitoring systems that monitor handwashing and equipmentwashing are disclosed in copending U.S. patent application Ser. No.09/699,796, filed Oct. 30, 2000 and are exemplary embodiments of theactivity based tracking method 100. In particular, the hygienemonitoring systems receive information indicative of the location ofcaregivers and handwashing devices and use/status information indicativeof the use of the handwashing devices. From this information, thehygiene monitoring systems determine whether caregivers need to washtheir hands to maintain compliance with an established hygiene policy.The disclosure of U.S. patent application Ser. No. 09/699,796, filedOct. 30, 2000 and entitled “Hygiene Monitoring System” is herebyincorporated by reference.

Referring now to FIG. 6, there is depicted an exemplary extubationprevention method 200 which is a particular embodiment of the ABT method150. Experience has shown that extubation is more likely if a patient islying against a side rail 26 of a bed 16 while on a ventilator 18.Extubation may result in harm to the patient and lost work time tore-establish the breathing pathway. When executing the extubationprevention method 200 of FIG. 6, the ABT system 10 generally determineswhether a patient is using a ventilator 18 while lying against a siderail 26 of a bed 16. If the patient is using a ventilator 18 while lyingagainst a bed side rail 26, then the ABT system 10 alerts a caregivervia a pocket pager, badge 12, or other portable device and may providethe caregiver with streaming video of the patient via the portabledevice or a nearby video display 28. With such information, thecaregiver determines whether corrective action is needed in order toprevent a possible extubation.

The master station 34 in step 202 receives location information frombadges 12 of tagged beds 16 and badges 12 of tagged ventilators 18 thatis indicative of the location of the tagged beds 16 and taggedventilators 18. The master station 34 in step 204 processes the locationinformation received in step 202 and updates location information forthe tagged beds 16 and ventilators 18.

The master station 34 of the ABT system 10 in step 206 receivesuse/status information from equipment sensors 24 of beds 16 andventilators 18 that is indicative of the use and/or status of the beds16 and ventilators 18. More specifically, the ABT system 10 in step 206receives use/status information from equipment sensors 24 of beds 16that is indicative of positions of patients within beds 16. In anexemplary embodiment, the beds 16 are equipped with one or moreequipment sensors 24 in the bed side rails 26 that detect the weight ofthe patient lying against the bed side rail 26. In an alternativeembodiment, the beds 16 include a patient support surface having onemore equipment sensors 24 that detect the position of the patient uponthe patient support surface as disclosed in U.S. Pat. No. 6,208,250,entitled “Patient Position Detection Apparatus for a Bed 16,” thedisclosure of which is hereby incorporated by reference.

The master station 34 in step 206 also receives use/status informationfrom equipment sensors 24 of ventilators 18 that is indicative of theusage of the ventilators 18. In an exemplary embodiment, the ventilators18 include one or more equipment sensors 24 that detect whether theventilator 18 is in use. For example, the ventilators 18 include acurrent sensor, voltage sensor, and/or power sensor which respectivelydetect the presence or absence of an operating current, operatingvoltage, and/or operating power and provide the result of such detectionto the master station 34. Numerous other manners for detecting whether adevice such as a ventilator 18 is operating are well known in the artand any may be used with the present invention.

The master station 34 in step 208 processes the use/status informationreceived in step 206 and updates use/status information for the beds 16and the ventilators 18 accordingly. More specifically, the masterstation in step 208 updates use/status information to indicate thecurrent position of patients in beds 16 and which ventilators 18 of theABT system 10 are presently being used.

The master station 34 analyzes the updated location and use/statusinformation to determine whether a patient has an increased likelihoodof extubation. More specifically, the master station 34 in step 210determines whether a patient is lying against a bed side rail 26 basedupon the use/status information associated with the beds 16. If themaster station 34 determines that a patient is not lying against a bedside rail 26, then the master station 34 returns to step 202 in order toprocess further information received from the badges 12 and theequipment sensors 24.

If the master station 34 determines that the patient is lying against abed side rail 26, then the master station 34 further determines whetherthe patient is using a ventilator 18. In particular, the master station34 determines whether a ventilator 18 is near the patient lying againstthe bed side rail 26 based upon location information associated with theventilators 18. In an exemplary embodiment, the master station 34determines that the ventilator 18 is near the patient if the locationinformation associated with the ventilator 18 indicates that theventilator 18 is in the same room as the patient lying against the bedside rail 26. Alternatively, the master station 34 may determine thatthe ventilator 18 is near the patient if the location informationindicates that the ventilator 18 is within a predetermined range (e.g.,3 feet) of the patient or the bed 16 on which the patient is lying.

If the master station 34 determines that a ventilator 18 is not near thepatient lying against the bed side rail 26, then the master station 34returns to step 202 in order to process further information receivedfrom the badges 12 and the equipment sensors 24. However, if the masterstation 34 determines that a ventilator 18 is near the patient lyingagainst the bed side rail 26, then the master station 34 in step 214determines whether the ventilator 18 near the identified patient is inuse based upon the use/status information associated with the ventilator18.

If the master station 34 determines that the ventilator 18 is not inuse, then the master station 34 returns to step 202 in order to processfurther information received from the badges 12 and the equipmentsensors 24. However, if the master station 34 determines that theventilator 18 is in use, then the master station 34 causes actionsassociated with preventing extubation of the identified intubatedpatient lying against the bed side rail 26. In an exemplary embodiment,the master station 34 in step 216 activates a camera 32 located in theroom of the identified patient and focuses the camera 32 on the patientif not already focused on the patient. The master station 34 in step 218identifies which caregiver is assigned to the identified patient basedupon patient assignment data that the master station 34 either maintainsor has access to.

The master station 34 in step 220 sends an extubation preventionnotification to the caregiver assigned to the intubated patient lyingagainst the bed side rail 26. More specifically, the master station 34causes the badge 12 of the identified caregiver to provide a tactileindication (e.g., vibrate), an audible indication (e.g., beep), a visualindication (e.g., blinking LED), and/or some other indication of thepossible extubation situation. Furthermore, the master station 34provides the identified caregiver with streaming video of the patientvia a hospital network system such as the system disclosed in U.S. Pat.Nos. 5,561,412, 5,699,038, and 5,838,223, the disclosures of which arehereby incorporated by reference. The streaming video enables thecaregiver to assess the patient specific situation to determine withoutphysically entering the room of the patient if intervention is required.If the streaming video indicates that intervention is not required, thenthe caregiver is saved a trip to the patient's room thus providing asavings of time. In an exemplary embodiment, the master station 34causes the video stream be sent to a video display 28 located near thecaregiver (such as a nurse's station, hall monitor, etc.) or to aportable pager or badge 12 carried by the caregiver which has videoplayback capabilities.

The master station 34 in step 222 determines whether an acknowledgmentwas received from the caregiver within a predetermined time span (e.g.,30 seconds). The ABT system 10 provides various manners for thecaregiver to acknowledge the extubation prevention notification. Forexample, the ABT system 10 enables caregivers to provide acknowledgmentsby actuating a mechanism (e.g., switch, button) on their badges 12, oractuating a nearby acknowledgment mechanism (e.g., switch, button)located in various locations throughout the facility such as in thepatient rooms, hallways, nurses station, rest rooms, utility rooms, etc.Alternatively, the ABT system 10 enables the caregiver to provide theacknowledgment via a remote control carried by the caregiver such as theremote control disclosed in U.S. patent application Ser. No. 09/848,941,entitled “Remote Control for Hospital Bed,” filed May 4, 2001, thedisclosure of which is hereby incorporated by reference.

If the master station 34 determines that an acknowledgment was notreceived from the caregiver within the predetermined timeout period,then the master station 34 in step 224 identifies another caregiverassigned to the patient. The master station 34 then returns to step 220in order to send an extubation prevention notification and accompanyingvideo stream to the newly identified caregiver. However, if the masterstation 34 determines that an acknowledgment was received from thecaregiver within the predetermined timeout period, then the masterstation 34 in step 226 deactivates the extubation preventionnotification and updates use/status information associated with thepatient and/or the ventilator 18 such that another extubation preventionnotification is not generated for the same patient for a predeterminedtime span (e.g., 5 minutes). The master station 34 then returns to step202 in order to process further information received from the badges 12and the equipment sensors 24.

Referring now to FIG. 7, there is depicted an exemplary fall preventionmethod 250 which is another exemplary embodiment of the ABT method 100.Experience has shown that a patient is more likely to fall out of a bed16 if a side rail 26 of a bed 16 is in a lowered position (i.e., down).When executing the patient fall prevention method 250 of FIG. 7, the ABTsystem 10 generally detects the position of a patient in a bed 16 andthe position of the side rails 26 of the bed 16. If ABT system 10detects that a bed side rail 26 is in a lowered position and the patientis lying near or is moving toward the lowered bed side rail 26, then theABT system 10 provides a caregiver with a fall prevention notificationvia a pocket pager or badge 12 and provides the caregiver with streamingvideo of the patient via a pocket pager, badge 12, or other portabledevice, or a nearby video display 28. With such information, thecaregiver can assess whether corrective action is needed in order toprevent a possible fall.

The master station 34 in step 252 receives location information frombadges 12 of tagged patients and badges 12 of tagged beds 16 that isindicative of the location of the tagged patients and beds 16. Themaster station 34 in step 254 processes the location informationreceived in step 252 and updates location information for the taggedpatients and beds 16 accordingly.

The master station 34 in step 254 receives use/status information fromequipment sensors 24 of the beds 16 that is indicative of the positionof a patient within a bed 16 and the position of bed side rails 26. Asindicated above, the beds 16 include a patient support surface havingone or more equipment sensors 24 that detect the position of a patientupon the patient support surface as disclosed in U.S. Pat. No.6,208,250. Moreover, the bed side rails 26 include one or more equipmentsensors 24 that detect the position of the side rail 26 and provideinformation indicative of the detected position of the bed side rail 26.In an exemplary embodiment, the bed side rails 26 are implemented asindicated in U.S. Pat. No. 6,021,533, filed on Aug. 25, 1992 andentitled “Mattress Having a Siderail Down Sensor,” the disclosure ofwhich is hereby incorporated by reference.

The master station 34 in step 258 processes the use/status informationreceived in step 256 and updates use/status information for the beds 16and the bed side rails 26 accordingly. More specifically, the masterstation in step 258 updates use/status information that indicates theposition of patients on beds 16 and the position of bed side rails 26.

The master station 34 analyzes the updated location and use/statusinformation to determine whether a patient has an increased likelihoodof falling from a bed 16. More specifically, the master station 34 instep 260 determines whether a bed side rail 26 is lowered based upon theuse/status information received from the bed side rails 26 in step 256.If the master station 34 determines that a bed side rail 26 is not inthe lowered position (i.e., determines that the bed side rail 26 is inthe raised position), then the master station 34 returns to step 252 inorder to receive and process further location and use/statusinformation. However, if the master station 34 determines that a bedside rail 26 is in the lowered position, then the master station 34proceeds to step 262 in order to determine whether a patient is lyingnear or is moving toward a lowered bed side rail 26.

In step 262, the master station 34 analyzes the use/status informationindicative of the position of patients within beds 16 in order todetermine whether a patient is lying near or is moving toward theidentified lowered bed side rails 26. If the master station 34determines that a patient is not lying near and is not moving toward alowered bed side rail 26, then the master station 34 returns to step 252in order to process further location and/or use/status information.

However, if the master station 34 determines that the patient is lyingnear or is moving toward a lowered bed side rail 26, then the masterstation 34 causes actions associated with preventing the identifiedpatient from falling from bed 16. In an exemplary embodiment, the masterstation 34 in step 264 activates a camera 32 located in the room of theidentified patient and focuses the camera 32 on the patient if notalready focused on the patient. The master station 34 in step 266identifies which caregiver is assigned to the identified patient basedupon patient assignment data that the master station 34 either maintainsor has access to.

The master station in step 268 sends a fall prevention notification tothe caregiver assigned to the patient lying near or moving toward thelowered bed side rail 26. More specifically, the master station 34causes the badge 12 of the identified caregiver to provide a tactileindication (e.g., vibrate), an audible indication (e.g., beep), a visualindication (e.g., blinking LED), and/or some other indication of thepossible fall situation. Furthermore, the master station 34 provides theidentified caregiver with streaming video of the patient via a hospitalnetwork system such as the system disclosed in U.S. Pat. Nos. 5,561,412,5,699,038, and 5,838,223. In an exemplary embodiment, the master station34 causes the video stream be sent to a video display 28 located nearthe caregiver (such as a nurse's station, hall monitor, etc.) or to aportable pager or badge 12 carried by the caregiver which has videoplayback capabilities.

The master station 34 in step 270 determines whether an acknowledgmentwas received from the caregiver within a predetermined timeout period(e.g., 30 seconds). The ABT system 10 provides various manners for thecaregiver to acknowledge the fall prevention notification. For example,the ABT system 10 enables caregivers to provide acknowledgments byactuating a mechanism (e.g., switch, button) on their badges 12 oractuating a nearby acknowledgment mechanism (e.g., switch, button)located in various locations throughout the facility such as in thepatient rooms, hallways, nurses station, rest rooms, utility rooms, etc.

If the master station 34 determines that an acknowledgment was notreceived from the caregiver within the predetermined timeout period,then the master station 34 in step 272 identifies another caregiverassigned to the patient. The master station 34 then returns to step 268in order to send a fall prevention notification and accompanying videostream to the newly identified caregiver. However, if the master station34 determines that an acknowledgment was received from the caregiverwithin the predetermined timeout period, then the master station 34 instep 274 deactivates the fall prevention notification and updatesuse/status information associated with the patient, the bed 16, and/orbed side rails 26 such that another fall prevention notification is notgenerated for the same patient for a predetermined time span (e.g., 5minutes). The master station 34 then returns to step 252 in order toprocess further location and/or use/status information.

Referring now to FIG. 8, there is provided an automated method 300 forgathering information about an activity or processes in a healthcarefacility and analyzing the gathered information with a simulationmodeling (“SM”) tool such as a dynamic simulation modeling tool or astatic simulation modeling tool. SM tools enable simulations of therelationships among various processes competing for space, time andresources and enable a quantitative assessment of the impact of proposedchanges. However, such SM tools require an extensive amount of dataassociated with the activities and processes to be simulated andanalyzed. Due to the costs associated with traditional methods forobtaining sufficient information regarding activities and processes, SMtools have not been utilized in the healthcare industry. The ABT system10 greatly reduces the cost of information gathering thus making itfeasible to apply SM tools and technology to the healthcare industry.

The automated method 300 of FIG. 8 is illustrated and described inregards to gathering and analyzing information regarding the process oftransferring a patient from one location to another location. However,those skilled in the art should readily appreciated that similartechniques apply to gathering and analyzing information about otherprocesses.

In step 302, the ABT system 10 receives information indicative of thestart of the process to be recorded. For example, in the case oftracking a patient transfer, the ABT system 10 receives informationdescribing a patient transfer order that has been entered into the ABTsystem 10 or a clinical information system in communication with the ABTsystem 10 in response to a written transfer order of a physician. In analternative embodiment, the physician directly enters the patienttransfer order into the ABT system 10 or the clinical information systemin communication with the ABT system 10 via a point of care computersystem.

The ABT system 10 begins to record information related to the monitoredactivity or process. In particular, the ABT system 10 in step 304 startstracking the length of time to complete the patient transfer. Forexample, the ABT system 10 records the time at which the patienttransfer order was received, records the time at which the patienttransfer order was written by the physician, begins a timer in responseto receiving the patient transfer order, and/or utilizes some othermechanism to track the length of time to complete the patient transfer.

The ABT system 10 also tracks and records the location and movement pathof tagged objects associated with the monitored activity. In particular,the ABT system 10 in step 306 monitors the location of the patient to betransferred based upon location information received from the badge 12of the patient. Further, the ABT system 10 in step 306 continuouslyupdates a graphical depiction of the current location of the patientupon one or more video displays 28. The ABT system 10 causes one or morevideo displays 28 to provide further visual indications that a transferis taking place such as (i) causing textual information indicative ofthe transfer to be displayed on video displays 28 (e.g., text in thescoreboard areas), and/or (ii) causing the graphical depiction of thepatient and/or the room in which the patient is to be transferred fromto be altered (e.g., blink, change color).

In step 308, the ABT system 10 determines whether the patient has leftthe room based upon location information received from the badge 12 ofthe patient. If the ABT system 10 determines that the patient has notleft the room, then the ABT system 10 returns to step 306 in order tofurther update the location of the patient. However, if the ABT system10 determines that the patient has left the room, then the ABT system 10in step 310 determines whether a caregiver is accompanying the patientbased upon location information received by the badges 12 of thecaregivers. If the ABT system 10 determines that a caregiver is notaccompanying the patient, then the ABT system 10 returns to step 306 inorder to further update the location of the patient.

The ABT system 10 in step 312 records which tagged objects (i.e.,equipment, caregivers, etc.) are associated with the transfer of thepatient. In particular, the ABT system 10 (i) determines based upon thelocation information received from badges 12 which caregivers are takingpart in the transfer of the patient and which equipment is beingtransferred with the patient, and (ii) records identificationinformation associated with such tagged objects. In an exemplaryembodiment, the ABT system 10 determines which equipment is beingtransferred with the patient based upon information received from badges12 of the equipment and business logic of the master station 34.Alternatively, equipment may be manually associated with a patient via aterminal (not shown) of the ABT system 10, thus providing the ABT system10 with an indication of which equipment needs to be tracked when thepatient is transferred.

The ABT system 10 in step 314 tracks the length of time the identifiedtagged objects are involvement with the patient transfer. In particular,the ABT system 10 records the time at which each identified taggedobject becomes involved with the patient transfer and records the timeat which each identified tagged object becomes no longer involved withthe patient transfer. Alternatively, the ABT system uses individualtimers for each of the identified tagged objects or some other mechanismin order to track the objects involvement. In general, the ABT system 10tracks the elapsed time of the patient from source (i.e., original room)to destination (i.e., new room), tracks the time of involvement of eachperson 14 involved with the transfer, and tracks the time of involvementfor each piece of equipment involved with the transfer.

The ABT system 10 in step 316 records the movement of the patient,caregivers, and equipment associated with the patient transfer. Theexemplary ABT system 10 periodically receives location information fromthe badges 12 of each tagged object on relatively short time intervalssuch as every 5 seconds. However, in order to reduce the amount oflocation information recorded, the ABT system 10 of the exemplaryembodiment stores the location of each patient, caregiver, and equipmentassociated with the transfer on a longer time interval such as every 10seconds. In an exemplary embodiment, the longer time interval used byABT system 10 is user definable for each monitored activity in order toenable user selectable granularity of the movement path of the patient,caregivers, and equipment associated with a particular activity.

The ABT system 10 in step 318 determines based upon location informationfor the patient whether the patient has returned to the original roomwithout being transferred to another room. If the ABT system 10determines that the patient has been returned to the original room, thenthe ABT system 10 in step 320 stops monitoring the movement path andelapsed times of the identified tagged objects and returns to step 306without saving the acquired information. However, if the ABT system 10determines that the patient has been transferred to another room, thenthe ABT system 10 in step 324 stores the acquired information (i.e.,elapsed times, movement, etc.) in a database.

The ABT system 10 then in step 326 utilizes SM tools to performcalculations on the information stored in the database. For example, theSM tools analyze the information to identify bottlenecks, resourcesconsumed, critical paths, etc., related to transfers based uponinformation gathered over a predetermined time period. The ABT system 10in step 328 updates information on the video displays 28 in order toindicate results of the SM tool analysis. For example, the ABT system 10causes the video displays 28 to provide statistical information relatedto the monitored activity such as the number of transfers, the totalcost of transfers, and personnel hours consumed due to transfers.Moreover, the ABT system 10 further causes the graphical depiction ofrooms associated with awaiting transfers to blink, and causes thegraphical depiction of hallways associated with bottlenecks in thephysical transfer to blink red.

Referring now to FIG. 9, there is shown an exemplary graphical display350 generated by the activity based tracking system 10 on video displays28. In the exemplary embodiment, the exemplary graphical display 350 isimplemented as a MedModel application executing on the master station34. MedModel is a software tool of ProModel Corporation which isgenerally used for simulation modeling of healthcare facilities. Thegraphical display 350 includes a floor layout 352 and a scoreboardstatus 354. The floor layout 352 depicts the physical features of thefacility (i.e., location of walls, rooms, doorways, etc.) and thelocation of tagged objects (e.g., beds 16, ventilators 18, persons 14).As indicated above, the master station 34 causes the floor layout 352 toprovide visual indications of monitored activities (e.g., causes rooms,persons 14, and/or equipment associated with a monitored activity to behighlighted, to be depicted in a different color, or to blink on andoff.)

The scoreboard status 354 generally provides pseudo-real time statisticsand other information for the facility and activities monitored in thefacility. For example, the master station 34 as a result of monitoringpatient transfers displays the total number of patient transfers, thetotal cost of patient transfers, personnel hours consumed due to patienttransfers, and/or other statistical information associated with patienttransfers over a certain time period.

In one embodiment, the locating system of ABT 10 compares the locationof an asset to expected locations of the asset and provides anindication to a caregiver or initiates an alarm if the location of theasset is an unexpected location. For example, if the asset is a patient,the locating system or ABT 10 expects that badge 12 corresponding to thepatient will most likely always be at least about three feet above thefloor in patient room A shown in FIG. 1. As such, if the location of thepatient (i.e., badge 12) is determined to be less than about three feetfrom the floor, the locating system or ABT 10 initiates an alarm orprovides an indication to a caregiver that the patient has fallen or islying on the floor. By knowing that the previous location of the patientwas in bed 16, the locating system or ABT 10 may determine that thepatient has fallen out of bed.

In one variation, the locating system ABT 10 waits a predetermined timeperiod to determine if the location of the asset returns to an expectedlocation before initiating an alarm or providing an indication to acaregiver. The length of the predetermined time period is selected tominimize false alarms triggered by a patient retrieving an article fromthe floor or engaging in other everyday activities. In anothervariation, the status of siderail 26 further assists in determining if apatient has exited bed 16 or fallen. In yet another variation, theacceleration data from badge 12 is used to distinguish between normalmovement and a fall (sudden change in acceleration, see FIG. 3B).

In one example, the type of asset governs the expected locations of theasset. For instance, it is known by the locating system ABT 10 thatbadge 12 when corresponding to an I/V pole (not shown) is always placedapproximately three feet from the base of the I/V pole. As such, anyaltitude deviation beyond a preset altitude deviation from thedetermination that the badge corresponding to the I/V pole isapproximately three feet from the floor results in the initiation of analarm or an indication to a caregiver. Further, an altitude deviationfrom the preselected altitude deviation may indicate that the asset (I/Vpole, ventilator, computer, etc.) has been dropped and must therefore berecertified. In one variation, the displacement sensor 50 of badge 12provides acceleration data which assists the locating system or ABT 10to distinguish between a situation wherein the asset has been placed onthe floor and a situation wherein the asset has been dropped.

In one example, the locating system or ABT 10 uses both statusinformation of equipment or personnel along with location information tobetter determine whether the location of the asset corresponds to anexpected location. For example, a bed such as bed 16 provides a statussignal indicating that the patient is lying on bed 16. As such, alocation determination which indicates that the patient is less thanabout three feet from the floor might correspond to a patient lying inbed 16 when bed 16 is positioned in a low configuration, not that thepatient has fallen.

In one embodiment, the locating system or ABT 10 determines, based onlocation information, the status of an asset. For example, based onlocation information, the locating system or ABT 10 may determine that awindow or a door is opened or closed.

In one embodiment, the locating system or ABT 10 prevents the movementof an asset based on the current location of at least one other asset.For example, based on the location of a monitor (not shown) relative tobed 16, the locating system or ABT 10 may prevent bed 16 from moving toa raised position or to a lowered position based on expectedinterference with the monitor. Once the monitor has been moved fartheraway from bed 16, the locating system or ABT 10 will allow the movementof bed 16 to a raised position or to a lowered position.

In one embodiment, ABT 10 is further configured to record locationinformation related to therapy. For example, a badge 12 may be attachedto a cast or sling for a patient lying in bed 16 or placed in traction.ABT 10 records the location of the cast or sling and maintains a recordof the locations of badge 12. Based on this information, a caregiver isbetter able to assess whether a patient is keeping the cast elevated fora given duration during the day or other activities.

In one embodiment, ABT 10 is configured to carry out activities based onthe location of an asset. For example, ABT 10 may be configured, suchthat once a caregiver enters a patient room a computer is booted oraccess to the computer is provided such that the caregiver can interfacewith patient care programs on the computer. Further, door locks may bedisabled or lighting adjusted based on the location of the caregiver inthe patient room. Additionally, a nurse call indicator may beautomatically reset once the caregiver enters the room.

In one embodiment, a portable device 400 is provided to a person, suchas a caregiver. Referring to FIG. 10, portable device 400 includes acontroller 402, a memory 404, a display 405, and a transceiver 406.Portable device 400 is configured to generate a request signalrequesting the location of an asset and to receive a location signalincluding an indication of the location of the asset. Portable device400 may be a badge, generally similar to badge 12, a portable dataassistant, a cellular phone, a pocket PC, or other similar portabledevice.

Portable device 400 is configured to provide the associated person withinstructions to direct the person to the requested asset. In oneexample, portable device 400 provides at least one of audio and visualinstructions. The audio instructions are provided with an optionalspeaker 408. In another example, portable device 400 provides compasstype directions. For example, portable device 400 provides on display405 a direction-indicating symbol, such as an arrow that points in thedirection to travel along a route to reach the location of the asset. Anexemplary system for directing a person to a specified location in afacility with a portable device is provided in application Ser. No.09/798,398, filed on Mar. 2, 2001, now U.S. Pat. No. 6,622,088 andtitled “AMBULATORY NAVIGATION SYSTEM,” the disclosure of which isexpressly incorporated herein by reference.

In one example, display 405 provides a map of the facility. The mapprovides an indication of the location of the portable device, thelocation of the requested asset, and a suggested route to the asset. Inone example, the route to the asset is shown in a different color thanthe rest of the map. Further, the suggested route may be chosen based onthe shortest distance or the shortest time to the asset. The shortesttime, in one example, being determined based on the potential congestionin various locations along potential routes.

In one example, the asset is in a location to which the user of theportable device does not have access. In such a case, the portabledevice 400 may direct the user of the portable device to a location thatis not the current location of the asset. For example, wherein the assetis a piece of equipment which must be checked out from an equipmentroom, the portable device 400 directs the user to a clerk associatedwith the equipment room. In another example, wherein the asset is apatient currently in surgery, the portable device 400 directs the userto a waiting room assigned to the surgical area wherein the patient islocated. Additionally, the portable device may communicate to the userthat the patient is still in surgery. The user may then add the asset toa watch list which instructs the portable device 400 to request updatesregarding the location of the asset and to provide instructions or anindication when the patient has left surgery and is in recovery.

In one embodiment, the map is a three-dimensional map. In one example,the three-dimensional map changes as the user of portable device 400progresses through the facility. For example, as the user walks forwardthe map progresses forward to show the environment corresponding to thelocation of the user. In one case, as the user approaches a bank ofelevators, the elevators appear on the three-dimensional map. Further,the map may include tagged assets along the route such as beds,caregivers, and equipment that are shown based on the current locationof such tagged assets.

The portable device 400 further includes an input device 410 whichallows the user to enter information such as a request for a specificasset or type of asset. Example input devices include a touch screen, atouch pad, a mouse, a light pen, a roller ball, a keyboard, a keypad, orone or more input keys. Assuming a user enters a request for an asset,ABT 10 locates the asset using the associated locating system and, basedon an indication that the asset is available, issues a command to havethe asset brought to the requested location. The command issued by ABT10 may result in an orderly being called to retrieve the asset or theactivation of a robot unit to retrieve the asset. In another example,the user also enters a requested destination location for the asset. Inanother example, the requested destination location is the location ofthe user at the time the request is made.

In one embodiment, the ABT system 10 provides a virtual facilitycorresponding to the actual facility that contains ABT 10. The virtualfacility includes representations of the various assets having badges 12associated therewith and physical structures, such as walls, elevators,cafeterias, and restroom facilities to name a few. In one example, therepresentations of the assets are selected from a library of imagescorresponding to various assets. For example, bed 16 may have multipleimages associated therewith, one corresponding to bed 16 being in a lowposition and another corresponding to bed 16 having a raised headsection. The images stored in the image library may be selected fromtwo-dimensional images and three-dimensional models, such as models foruse by a VRML (virtual reality modeling language) based system.

The images corresponding to the assets are located in the virtualfacility based on their current locations as recorded by the locatingsystem associated with ABT 10. Further, the images may be animated tosimulate movement or use. For example, a person walking in the facilitymay be animated in the virtual facility to simulate walking. Also, ifthe person associated with badge 12 has an associated personal image,such as the person's face then that image may be shown. In anotherexample, an I/V pump may include an animation to indicate that it iscurrently turned on and is pumping.

The virtual facility may be presented to a user or caregiver through avirtual facility interface, such as portable device 400, through acomputer interface located within the facility, such as at a caregiverstation or in a patient room, or through a virtual reality systemincluding goggles to be worn by the user. The virtual reality system, inone example, places the user in a three-dimensional representation ofthe facility.

Through the virtual facility interface the user may select an asset,such as bed 16. In one example, the user has the option to be presentedwith information related to the asset, such as maintenance records,specifications, manuals, status, history, prior locations, and otherasset related information. In another example, the user can obtaininformation related to an alarm status associated with the asset. In yetanother example, the user may change the status of the asset. Forinstance, a caregiver may send a signal to bed 16 to raise siderail 26.As such, the caregiver may remotely change the status or configurationof an asset via the virtual reality interface.

In one embodiment, the virtual reality interface color-codes assetsbased on their status. For example, bed 16 may be shown in red if analarm is associated with bed 16 or bed 16 may be shown in yellowindicating that bed 16 needs attention, such as a linen change. Further,assuming the user of virtual reality interface has a badge associatedtherewith, the user may receive status information abouthimself/herself. For example, the user might be shown in red if the useris currently contaminated and needs to wash his or her hands. Details onwhat constitutes a contamination and methods and apparatuses formonitoring handwashing are disclosed in copending U.S. patentapplication Ser. No. 09/699,796, filed Oct. 30, 2000 which is expresslyincorporated by reference.

FIGS. 11–23 provide additional exemplary locating and tracking systemsfor use with ABT system 10. Many of the following locating and trackingsystems are configured to determine the location of an asset and/or totrack the location of the asset through use of various transceiverslocated throughout a facility and badges associated with the assets. Thebadges are configured to generate an ID signal that provides anindication of the asset associated with the respective badge. Further,each of the locating and tracking systems is configured to beimplemented as part of ABT system 10 or as stand-alone location andtracking systems.

It should be noted that the concepts described in each locating systemcan be combined with the concepts of the other locating systems tocreate hybrid-type locating systems. For instance, each of the exemplarylocating systems can include ARP sensors 20 or ARP-style transmitterspositioned at various locations, such as in doorways or other locations.

In one example, the location of an asset is determined by identifyingwhich transceiver receives an ID signal from a badge associated with theasset. An infrared (IR) line-of-sight tracking system is one type ofsuch locating and tracking system. Another type is the passive RFtransmitters and ARP sensors 20 discussed above. The system knows thatthe asset is generally in the area of the transceiver receiving thesignal from the badge. In one variation, signal strength of the IDsignal received from the badge is used to better approximate thelocation of the corresponding asset relative to the transceiver, asfurther described below. In another variation, the badge is interrogatedor caused to send the ID signal and the time it takes for the signal toreach the transceiver is used to better approximate the location of thecorresponding asset relative to the transceiver, as further describedbelow.

In another example, the location of an asset is determined by two ormore fixed-location transceivers that each receive an ID signal from thebadge associated with the asset. Such systems determine the location ofthe asset by determining a distance measurement for each transceiverthat is indicative of the distance from the respective transceiver tothe badge. The distance measurements for the transceivers are then usedto determine the location of the asset in either two dimensions or threedimensions. In one variation, the distance measurements are based on thetime it takes for the ID signal from the badge to reach eachtransceiver. In another variation, the distance measurements are basedon the signal strength of the ID signal received at each transceiver. Inyet another variation, the distance measurements are based on acombination of both time and signal strength. The location of the assetmay be classified as being within a given region or zone of an area ofinterest or as being within a sphere of space having a center thatcorresponds to the best approximation of the asset location and aperiphery corresponding to the resolution of the system.

In yet another example, the location of an asset is determined based onlocation signals sent by a badge to a central receiver. In this example,the badge receives signals from at least one of the fixed transmitters,each of the fixed transmitters generating a unique ID signal. The badgethen either generates a location signal including the receivedtransmitter ID along with an ID associated with the badge to the centralreceiver or determines its own location and generates a location signalincluding the determined location and the associated badge ID to thecentral receiver. Either way the location of the badge is determinedbased at least in part on the received transmitter IDs. In onevariation, the location of the badge is determined based on the receivedtransmitter IDs. In another variation, the location of the badge isdetermined based on the received transmitter IDs and at least one ofsignal strength or timing information.

Referring to FIG. 11, one exemplary locating and tracking system 500 ofthe present invention is shown. System 500 includes a badge or tag 502,which is attached to or otherwise associated with an asset 504, threefixed transceivers 506, 508, 510 mounted at known locations within anarea 512 such as a hospital room, and a central computing device 514,such as master station 34, connected to transceivers 506, 508, 510 via awired or wireless connection referred to by the numeral 516. In oneexample, locating system 500 including one or more ARP sensors 20 whichare located at various locations, such as proximate a doorway 519, andare connected to central computing device 514.

Badge 502 is generally similar to badge 12 and includes at least one ofa passive RFID transmitter, an active RF transmitter, an active IRtransmitter, an ultrasound transmitter, or other suitable transmitterconfigured to emit or generate an identification (ID) signal travelingin free space. Transceivers 506, 508, 510 each include a sensor todetect the ID signal being generated by badge 502 and/or to excite badge502 to generate the ID signal. It should be noted that the termtransceiver is used to denote devices at least configured to receive anID signal from a badge, such as badge 502. Further, as explained herein,in some embodiments and examples the transceivers are further configuredto transmit an excitation signal which is received by the badges and inturn causes the badges to transmit an ID signal.

In one embodiment, badge 502 includes an active RF transmitter (notshown) that transmits an ID signal uniquely associated with the asset504. Power may be supplied to badge 502 by a battery (not shown) as iswell known in the art. In another embodiment, badge 502 may furtherinclude an antenna (not shown) that receives an excitation signal from atransceiver 506, 508, 510 when within the range of the transceiveraccording to conventional techniques. The same antenna may be used totransmit the ID signal associated with badge 502. Badge 502 in oneexample is an RFID tag which provides an ID signal associated with asset504 in response to receiving an excitation signal from at least one oftransceivers 506, 508, 510. As such, badge 502 may be configured to emitan ID signal at a predetermined time interval, to emit an ID signal atrandom time intervals, to emit an ID signal at varying time intervalsbased on a characteristic of asset 504, or in response to the receptionof an excitation signal. In one example, badge 502 includes adisplacement sensor and badge 502 transmits its associated ID signal attwo or more transmission rates depending on the output of thedisplacement sensor.

When badge 502 is configured to generate or emit the ID signal at apredetermined interval, transceivers 506, 508, 510 are configured todetect the emission of the ID signal. However, when badge 502 isconfigured to emit the ID signal in response to reception of anexcitation signal, transceivers 506, 508, 510 are configured to transmitan excitation signal that has sufficient strength to be received bybadge 502 anywhere within area 512. As such, transceivers 506, 508, 510include at least one of an RFID exciter, a RF receiver, an RFtransmitter, an RF transceiver, an IR receiver, an IR transmitter, an IRtransceiver, an ultrasound receiver, an ultrasound transmitter, or othersuitable receivers, transmitters, or transceivers configured to receiveID signals from badge 502 and/or configured to cause badges 502 togenerate and transmit an ID signal.

Each transceiver 506, 508, 510 further includes a detection circuit (notshown) that performs a badge locating function as is further describedbelow. The badge locating function corresponds to the calculation of adistance measurement associated with badge 502. As stated above andexplained in more detail below, the distance measurement for a givenbadge is based on at least one of signal strength or timing information.

In operation, an asset 504 having a badge 502 associated therewith movesinto area 512. Assuming badge 502 generates the corresponding ID signalin response to an excitation signal, when asset 504 enters area 512, theantenna of asset 504 receives excitation signals from at least one oftransceivers 506, 508, 510. Badge 502 responds to receipt of anyexcitation signal by transmitting its ID signal via its antenna.Alternatively, badge 502 includes an active RF transmitter and transmitsthe associated ID signal at a predetermined time interval or a randomtime interval. As such, transceivers 506, 508, 510 do not need to sendexcitation signals to initiate transmission of the ID signal from badge502. In one example, badge 502 includes a motion detector ordisplacement sensor and the transmission rate of the ID signal isdependent upon the status of the motion detector or displacement sensor.

When badge 502 transmits its ID signal either due to reception of anexcitation signal or at a predetermined or random time interval,transceivers 506, 508, 510 receive the ID signal, process it, andtransmit location signals to central computing device 514. In oneexample, transceivers 506, 508, 510 are all positioned in room 512 atapproximately the same height or altitude. In another example, at leastone of transceivers 506, 508, 510 is positioned at a different height oraltitude than the remaining transceivers 506, 508, 510.

Referring to FIGS. 11–13C, each transceiver 506, 508, 510 or centralcomputing device 514 determines based at least in part on the receivedID signal from badge 502 a distance measurement 524, 526, 528corresponding to the respective transceiver 506, 508, 510. The distancemeasurement corresponds to the distance between badge 502 and therespective transceiver 506, 508, 510. As illustrated in FIG. 11, badge502 generates an ID signal 518 which is detected by transceivers 506,508, 510. Illustratively, transceiver 506 detects ID signal 518A,transceiver 508 detects ID signal 518B, and transceiver 510 detects IDsignal 518C. It should be noted that ID signals 518A, 518B, 518C allcontain the same information, however, each may have different signalstrengths due to the distance between badge 502 and transceivers 506,508, 510. Referring to FIG. 13A, ID signal 518A corresponding totransceiver 506 results in a calculated distance measurement 524 ofthree feet, ID signal 518B corresponding to transceiver 508 results in acalculated distance measurement 526 of eight feet, and ID signal 518C totransceiver 510 results in a distance measurement 528 of ten feet. Inone embodiment, distance measurements 524, 526, 528 are calculated byeither the respective transceiver 506, 508, 510 or the central computingdevice 514. In other embodiments, the distances are calculated by 502and transmitted to transceivers 506, 508, 510.

Once the distance measurements have been calculated central computingdevice 514 may access stored location information corresponding to thefixed locations of transceivers 506, 508, 510 and apply knownmathematical techniques to determine a location of asset 504. In athree-dimensional system, illustratively shown in FIG. 12, centralcomputing device 514 determines that asset 504 is located a distance507, from wall 520 of area 512, such as five feet, a distance 509, fromwall 522, such as five feet, and a distance 511 above floor 521, such asfour feet. In a two-dimensional system, central computing device 514will apply known mathematical techniques to determine that asset 504 isa distance 507 from wall 520 of area 512 and a distance 509 from wall522 of area 512. As asset 504 moves within area 512, the above-describedprocess is periodically repeated to maintain up-to-date locationinformation relating to asset 504. The example illustrated in FIG. 12shows the distance information in Cartesian coordinates. However, it iswithin the scope of the present invention to report location informationin other formats, including a zone designation or spherical coordinates.

In one three-dimensional embodiment, locating system 500 uses simpletriangulation to determine the location of asset 504 based on distancemeasurements 524, 526, 528. FIG. 13A corresponds to a diagrammatic viewof a plane generally parallel to floor 521 and coincident to an altitudeof asset 504. As shown in FIG. 13A, distance measurement 524corresponding to transceiver 506 indicates that asset 504 isapproximately located on the circumference of a sphere 525 (shown as acircle in the plane shown in FIG. 13A) having a radius of three feetequal to distance measurement 524. Further, distance measurement 526corresponding to transceiver 508 indicates that asset 504 isapproximately located on the circumference of a sphere 527 (shown as acircle in the plane shown in FIG. 13A) having a radius of eight feetequal to distance measurement 526. As such, based on distancemeasurements 524 and 526, locating system 500 may narrow the location ofasset 504 to approximately a circle in three-dimensional space andeither location 530 or location 532 in the plane shown in FIG. 13A, bothof which are intersections of spheres 525 and 527. The ambiguity in thelocation of asset 504 is resolved by distance measurement 528corresponding to transceiver 510, which indicates that asset 504 isapproximately located on the circumference of a sphere 529 (shown as acircle in the plane shown in FIG. 13A) having a radius of ten feet equalto distance measurement 528. Sphere 529 most closely intersects withspheres 525 and 527 at location 530. Therefore, locating system 500 maydeduce that the location of asset 504 is location 530.

It should be understood that the location of asset 504 in at least oneinstance is determined by the closest positioning of spheres 525, 527,526 relative to each other because one or more of spheres 525, 527, 529does not intersect at least one of the other of spheres 525, 527, 529,or that the intersection of a first pair of spheres 525, 527, 529 doesnot coincide with the intersection of a second pair of spheres 525, 527,529. The determination of the location of asset 504 may be enhanced byadding additional transceivers to room 512, such as transceiver 534shown in FIGS. 11 and 13A, which is generally similar to transceivers506, 508, 510 and receives ID signal 518D from badge 502 of asset 504.Transceiver 534 provides an additional distance measurement 536 andcorresponding sphere 537 (shown as a circle in the plane shown in FIG.13A). By looking at the distance measurements 524, 526, 528, 536,locating system 500 can better pinpoint the location of asset 504. Forexample, the location of asset 504 can be determined using distancemeasurements 524, 526, 528, 536 and a least squares algorithm or otherknown mathematical techniques.

In one two dimensional embodiment, locating system 500 usestriangulation to determine the location of asset 504 based on distancemeasurements 524, 526, 528. FIG. 13B corresponds to a diagrammatic viewof a plane generally parallel to floor 521, and not coincident to analtitude of asset 504. It should be noted that if the plane of FIG. 13Bwas coincident to an altitude of asset 504, FIG. 13B would be identicalto FIG. 13A. However, the plane FIG. 13B was chosen to not be coincidentwith an altitude of asset 504 to better illustrate characteristics of atwo-dimensional location determination that does not account for thealtitude of an asset.

Referring to FIG. 13C, badge 502 transmits ID signal 518A to transceiver506. As shown in FIG. 13C, badge 502 is at a different altitude(represented by a distance 540) relative to floor 521 than transceiver506. Further, badge 502 in reality is located a distance 542 fromtransceiver 506. As such, based on either signal strength or timinginformation, or a combination of both signal strength and timinginformation, transceiver 506 or central computing device 514 willdetermine a distance measurement 524 generally equal in magnitude todistance 542.

Distance measurements 524, 526, 528 of transceivers 506, 508, 510,respectively, indicate that asset 504 is located as respective circles545, 547, 549. However, as shown in FIG. 13B, circles 545, 547, 549 donot intersect at generally the same location. This is due to the factthat distance measurements 524, 526, 528 include a componentcorresponding to the difference in altitude between badge 502 andrespective transceivers 506, 508, 510. As such, assuming that badge 502is at a different altitude than all of respective transceivers 506, 508,510, each distance measurement 544, 546, 548 will incorrectlyoverestimate a horizontal distance from respective transceiver 506, 508,510 to badge 502 such as horizontal distance 550 between transceiver 506and badge 502 as shown in FIG. 13C. In fact, distance measurement 544overestimates horizontal distance 550 by a distance 552.

Referring to FIG. 13B, locating system 500 may determine that thelocation of asset 504 is within a region 552 bounded by circles 545,547, 549. In one example, the location of asset 504 is assumed to be thecenter 538 of region 552. For some applications, the knowledge thatasset 504 is located within region 552 may be sufficient, while forother applications the extent of region 552 may need to be reduced toincrease the accuracy of the estimated location of asset 504. It shouldbe understood that if lower resolution is acceptable, only twotransceivers are required, such as transceivers of 506 and 508, andasset 504 is assumed to be located in region 553 (which includes region552) corresponding to the overlap of circles 545 and 547.

One method to reduce the extent of region 552 is to utilizecharacteristics of an asset to better estimate distance measurements544, 546, 548 or to modify distance measurements 544, 546, 548 toaccount for the altitude of badge 502. For instance, it might be knownthat all I/V poles have associated badges 502 placed three feet fromfloor 521. As such, when central computing device 514 receives a set ofdistance measurements, such as distance measurements 544, 546, 548,corresponding to an I/V pole, central computing device 514 knows tomodify distance measurements 544, 546, 548 to account for differences inaltitude between badge 502 and respective transceivers 506, 508, 510.Referring to FIG. 13C, central computing device 514 will modify distancemeasurement 544 to be generally equal to distance 550 with knowntrigonometric relations by knowing measured distance measurement 544 andby knowing distance 540.

In one variation of system 500, the detection circuit of eachtransceiver 506, 508, 510 includes a signal strength detector. As such,each detection circuit includes electronics for determining the strengthof ID signals received from badges 502. Transceivers 506, 508, 510 inthis variation of system 500 may further include electronics and/orsoftware for converting the determined signal strength into a distancemeasurement, which is communicated to central computing device 514 forprocessing. Alternatively, transceivers 506, 508, 510 may simplytransmit signal strength measurements to central computing device 514,which includes hardware and/or software for performing the conversion todistance.

In one example, the signal strength is converted to a distancemeasurement by comparing the received signal strength to known signalstrengths corresponding to known distances. In another example, thesignal strength is compared to the signal strength of fixed badges whoselocation and hence distance to transceivers 506, 508, 510 is known. Anillustrative fixed badge 560 is shown in FIG. 11. Fixed badge 560generates an ID signal 517 including a unique identifier associated withfixed badge 560. Transceiver 506, as representative of transceivers 506,508, 510, receives ID signal 517 and determines the signal strength ofID signal 517. Distance measurement 524 is determined by multiplying aratio of the signal strength of ID signal 518A and the signal strengthof ID signal 517 by the known distance to fixed badge 560. In one case,the distance measurement 524 is determined from the signal strength ofID signals from a plurality of fixed badges.

In yet another example, transceiver 506 sends out an excitation signalto badge 502 which generates an ID signal. The excitation signalincludes a unique identifier or ID associated with transceiver 506.Badge 502 is configured to determine the signal strength of the receivedexcitation signal. The ID signal generated by badge 502 includes the IDreceived from transceiver 506, an ID associated with badge 502, and thesignal strength of the received excitation signal. By including thereceived transceiver ID, transceivers 506, 508, 510 can determine towhich transceiver badge 502 is responding.

Transceiver 506 or central computing device 514 then computes, forexample, distance measurement 524 based either on the reported signalstrength of the excitation signal or the reported signal strength ofboth the excitation signal and the received ID signal. Either way, theabove-mentioned signal strengths are compared to either known signalstrengths or signals strengths from one or more fixed badges 560. In onecase, fixed badges 560 may also include in their ID signals the receivedtransceiver ID and the signal strength of the received excitationsignal.

In the example shown in FIG. 11, the ID signals received by transceivers506, 508, 510 are labeled 518A, 518B, and 518C, respectively. ID signal518A may be a relatively weak signal, or have a low signal strength, asdetected by transceiver 506 because of the relatively long distancebetween badge 502 and transceiver 506. ID signal 518C, on the otherhand, may be a relatively strong signal, or have a high signal strength,as detected by transceiver 510 because of the relatively short distancebetween badge 502 and transceiver 510. ID signal 518B may have a signalstrength that falls between the strengths of ID signals 518A and 518C.When the signal strengths are converted to distance measurements 524,526, 528, either by transceivers 506, 508, 510 or by central computingdevice 514, central computing device 514 may determine the location ofasset 504 by using the known locations of transceivers 506, 508, 510. Inone embodiment, locating system 500 determines the location of asset 504in two-dimensions, such as the location of asset 504 in area 512(without regard to altitude) as explained above in connection with FIGS.11, 13B and 13C. In another embodiment, locating system 500 determinesthe location of asset 504 in three-dimensions, such as the location ofasset 504 in area 512 and relative to floor 521 of area 512 as explainedabove in connection with FIGS. 11, 12, and 13A.

In another variation of system 500, the detection circuit of eachtransceiver 506, 508, 510 includes a timer circuit, electronics, such asfor determining the time required to transmit an excitation signal tobadge 502 and receive an ID signal in response. Transceivers 506, 508,510 in this variation of system 500 may further include electronicsand/or software for converting the determined time required to transmitan excitation signal to badge 502 and to receive an ID signal inresponse into a distance measurement which is communicated to centralcomputing device 514 for processing. Alternatively, transceivers 506,508, 510 may simply transmit the timing information to central computingdevice 514, which includes hardware and/or software for performing theconversion to a distance measurement. The calculated distancemeasurement includes a known badge delay, t_(BD), corresponding to thetime required for badge 502 to process the excitation signal andgenerate an ID signal.

FIGS. 14A–14B illustrate several examples of interactions betweentransceiver 506 and badge 502 for the calculation of distancemeasurement 524. It should be understood that the interactions betweenbadge 502 and transceivers 508 and 510 are generally similar to theinteractions between badge 502 and transceiver 506. Referring to FIG.14A, a first example of the interaction between badge 502 andtransceiver 506 is shown. As shown in FIG. 14A, transceiver 506generates a excitation signal 570 which is received by badge 502. In oneexample, excitation signal 570 includes an ID that is unique totransceiver 506. Badge 502 responds by generating an ID signal 518. Inone example, the badge ID signal 518 includes the received transceiverID and an ID that is unique to badge 502. By including the receivedtransceiver ID, transceivers 506, 508, 510 can determine to whichtransceiver badge 502 is responding.

The distance measurement calculated by either transceiver 506 or centralcomputing device 514, in one example, corresponds to equation 1 below,wherein D is the calculated distance measurement, < is the propagationspeed of the generated signals (IR, RF, ultrasound, etc.), t_(E) is thetime period for excitation signal 570 to reach badge 502, t_(BD) is thetime period for badge 502 to process excitation signal 570 and generateID signal 518, and t_(BT) is the time period for badge ID signal 518 toreach transceiver 506.

$\begin{matrix}{D = \frac{\upsilon( {t_{E} + ( {t_{BT} - t_{BD}} )} )}{2}} & (1)\end{matrix}$

As explained above in connection with FIGS. 12 and 13A–C, the distancemeasurements for each transceiver are used to estimate the location ofbadge 502 in either two-dimensional space or three-dimensional space.

In one example, transceiver 506 and badge 502 generate signals usingdifferent signal types. For example, transceiver 506 might generate anRF signal and badge 502 might generate an ultrasound signal. In such asituation, the propagation speed of each signal is different. Therefore,equation 1 must be modified to account for the different propagationspeeds. Equation 2 provides the distance measurement for the examplewhen transceiver 506 and badge 502 generate signals of differentpropagation speeds wherein <_(T) is the propagation speed of the signalgenerated by transceiver 506 and <_(B) is the propagation speed of thesignal generated by badge 502.

$\begin{matrix}{D = \frac{ {{\upsilon_{T}t_{E}} + {\upsilon_{B}( {t_{BT} - t_{BD}} )}} )}{2}} & (2)\end{matrix}$

Referring to FIG. 14B, a second example of the interaction between badge502 and transceiver 506 is shown wherein transceiver 506 does notgenerate an excitation signal 570. As such, transceiver 506 may be asimple receiver. As shown in FIG. 14B, a fixed location pinger(transmitter) 501 generates an excitation signal 574 which is receivedby both transceiver 506 and badge 502. In one example, a plurality offixed pingers, similar to fixed pinger 501, are provided. In oneexample, excitation signal 574 includes an ID that is unique to pinger501. In another example, excitation signal 574 includes a time-stamp. Inyet another example, excitation signal 574 includes both a unique pingerID and a time-stamp.

Badge 502 responds to the reception of excitation signal 574 bygenerating an ID signal 518. In one example, ID signal 518 includes anID that is unique to badge 502. In another example, ID signal 518includes a time-stamp. In yet another example, ID signal 518 includesboth a unique badge ID and a time-stamp. In a further example, ID signal518 includes at least one of a badge ID and a badge timestamp along withthe information or an indication of the information received inexcitation signal 574 selected from a pinger ID and a pinger timestamp.By including the received pinger ID or timestamp, transceivers 506, 508,510 can determine to which pinger signal(s) 574 badge 502 is responding.

Transceiver 506 receives both excitation signal 574 from pinger 501 andID signal 518 from badge 502. The distance measurement calculated byeither transceiver 506 or central computing device 514, in one example,corresponds to equation 3 wherein D is the calculated distancemeasurement, < is the propagation speed of the generated excitation andID signals (IR, RF, ultrasound), t_(PB) is the time period forexcitation signal 574 to reach badge 502, t_(BD) is the time period forbadge 502 to process excitation signal 574 and to generate ID signal518, t_(BT) is the time period for badge ID signal 518 to reachtransceiver 506, and t_(PT) is the time period for excitation signal 574to reach transceiver 506.D=v[(t _(PB)+(t _(BT) −t _(BD)))−t_(PT)]  (3)

As explained above in connection with FIGS. 12 and 13A–C, the distancemeasurements for each transceiver are used to estimate the location ofbadge 502 in either two-dimensional space or three-dimensional space.

In one example, pinger 501 and badge 502 generate signals usingdifferent signal types. For example, pinger 501 might generate an RFsignal and badge 502 might generate an ultrasound signal. In such asituation the propagation speed of each signal is different. Therefore,equation 3 must be modified to account for the different propagationspeeds. Equation 4 provides the distance measurement for the examplewhen pinger 501 and badge 502 generate signals of different propagationspeeds wherein <_(P) is the propagation speed of the signal generated bypinger 501 and <_(B) is the propagation speed of the signal generated bybadge 502.D=v _(P) t _(PB) +v _(B)(t _(BT) −t _(BD))−v _(P) t _(PT)  (4)

In one example, t_(BD) is set to be longer in duration than t_(PT) suchthat the dependence on t_(PB) in the calculation of D is reduced. In onecase t_(BD) is set equal to about five seconds.

Referring to FIG. 11, locating system 500, in one embodiment, includesat least one pinger 501 and transceivers 506, 508, 510. Transceivers506, 508, 510 are connected to central computing device 514 through awireless or wired connection. As shown in FIG. 11, asset 504 andassociated badge 502 enter area 512. Badge 502 receives an excitationsignal 574 from fixed pinger 501. Excitation signal 574, in one example,is generated at a predetermined time interval. In another example,excitation signal 574 is generated at two or more predetermined timeintervals including a first time interval corresponding to a highactivity time period, such as a day shift in a hospital ward, and asecond time interval corresponding to a lower activity time period, suchas a night shift in a hospital ward. In an alternative embodiment, atleast one of transceivers 506, 508, 510 generates excitation signal 574.As such locating system 500 does not need a separate fixed pinger.

Excitation signal 574 is received by badge 502 and transceivers 506,508, 510. Further, badge 502 generates ID signal 518 in response toexcitation signal 574 that is received by transceivers 506, 508, 510. Asexplained above, either transceivers 506, 508, 510 or central computingdevice 514 determines a distance measurement 524, 526, 528 correspondingto the distance from transceiver 506, 508 510 to badge 502.

In one example, transceivers 506, 508, 510 and badges 502 are timesynchronized (i.e., each precisely measures time from a common startinginstant). Fixed pinger 501 generates an excitation signal 574. Badge 502receives excitation signal 574 and generates ID signal 518 including atimestamp. ID signal 518 is received by transceivers 506, 508, 510.Transceivers record or otherwise denote the timestamp associated withthe generation of ID signal 518. Since transceivers 506, 508, 510, andbadges 502 are synchronized, by knowing the time ID signal 518 wasgenerated and the time it was received, each transceiver can estimate adistance measurement corresponding to the distance of badge 502 fromtransceiver 506, 508, 510, respectively. At least two transceivers oftransceiver 506, 508, 510 are needed to locate badge 502 in a twodimensional space, such as over floor 521 (without regard to altitude)as explained above in connection with FIGS. 11, 13B and 13C. At leastthree transceivers are needed to locate badge 502 in three dimensionalspace as explained above in connection with FIGS. 11, 12 and 13A. Thedetermination of the location of badge 502 may be further enhanced bythe implementation of additional transceivers, such as transceiver 534shown in FIG. 11. (It should be noted that the time period correspondingto the delay associated with badge 502 processing the receivedexcitation signal 574 and generating ID signal 518 is taken into accountby the transceiver 506, 508, 510 in calculating distance measurement524, 526, 528 for badge 502.)

In another example, transceivers 506, 508, 510, badges 502 and fixedpinger 501 are time synchronized. Excitation signal 574 generated byfixed pinger 501 includes a timestamp. Each of transceivers 506, 508,510 receive excitation signal 574 from pinger 501 and records orotherwise denotes the timestamp associated with excitation signal 574.Badge 502 receives excitation signal 574 and generates ID signal 518including a timestamp and the timestamp associated with reception ofexcitation signal 574. ID signal 518 is received by transceivers 506,508, 510. Transceivers record or otherwise denote the timestampassociated with the generation of ID signal 518. Since pinger 501,transceivers 506, 508, 510, and badges 502 are synchronized, by knowingthe time excitation signal 574 was sent, the time excitation signal 574was received by badge 502, and the time ID signal 518 was generated,each transceiver 506, 508, 510 may estimate a distance measurementcorresponding to the distance of badge 502 from the respectivetransceiver 506, 508, 510.

By determining the distance measurement during, for example, three timeperiods instead of one, a better approximation of the distance frombadge 502 to the respective transceiver can be made. Further, if theplacement of pinger 501 and the respective transceiver are known, theloci of possible locations of badge 502 may be reduced from generally asphere to generally a circle. At least two transceivers of transceiver506, 508, 510 are needed to locate badge 502 in a two dimensional space,such as a plane over floor 521 as explained above in connection withFIGS. 11, 13B, and 13C. At least three transceivers are needed to locatebadge 502 in three dimensional space as explained above in connectionwith FIGS. 11, 12, 13A. The determination of the location of badge 502may be further enhanced by the implementation of additionaltransceivers, such as transceiver 534 shown in FIG. 11. (It should benoted that the time period corresponding to the delay associated withbadge 502 processing the received excitation signal and generating theID signal is taken into account by the transceiver 506, 508, 510 incalculating the distance measurement 524, 526, 528 for badge 502.)

In another embodiment, transceivers 506, 508, 510 act as pingers andgenerate excitation signals which are received by badge 502 and by fixedbadges, such as fixed badge 560 in FIG. 11. Both badge 502 and fixedbadge 560 receive the generated excitation signals from transceivers506, 508, 510 and generate an ID signal 517, 518 corresponding to therespective badge 502, 560. In one example the transceiver excitationsignals include a transceiver ID and the badge ID signal signals includea badge ID and the received transceiver ID. By including the receivedtransceiver ID, transceivers 506, 508, 510 are able to determine towhich transceiver badges 502, 560 are responding.

A distance measurement for badge 502 is determined by transceivers 506,508, 510 by comparing the round trip time (from generation of theexcitation signal to reception of the respective ID signal) to receiveID signal 517 and the round trip time to receive ID signal 518. Asstated previously, the location of fixed badge 560 is known and hencethe round trip time corresponding to ID signal 517 may be equated to adistance value. Distance measurements 524, 526, 528 are determined bymultiplying a ratio of the round trip time of ID signal 518 and theround trip time of ID signal 517 by the known distance to fixed badge560.

In another embodiment shown in FIG. 15, a single transceiver orreceiver, such as transceiver 506, is provided in area 512 along withmultiple fixed pingers, such as pingers 501, 503, 505. Each pinger isconfigured to generate an excitation signal, such as excitation signal574, 576, 578, which is received by transceiver 506 and by a badge 502associated with asset 504. Each excitation signal 574, 576, 578 includesa unique ID to identify the respective pinger 501, 503, 505. Badge 502,in response to receiving an excitation signal, generates an ID signal518, which includes a unique ID associated with badge 502 and the uniqueID of the pinger or pingers 501, 503, 505 which generated the receivedexcitation signal.

In another example, badge 502 and fixed pingers 501, 503, 505 aresynchronized and each pinger 501, 503, 505 generates an excitationsignal 574, 576, 578 respectively. Excitation signal 574, 576, 578includes a unique ID associated with the respective pinger 501, 503, 505and a timestamp corresponding to the time of generation of theexcitation signal 574, 576, 578. Badge 502 receives the excitationsignals from each pinger 501, 503, 505 and determines a distancemeasurement between itself and pingers 501, 503, 505 and the location ofitself based on time between the generation of the respective excitationsignals 574, 576, 578 and the reception of the respective excitationsignals 574, 576, 578 and a knowledge of the location of the respectivepinger 501, 503, 505. At least two pingers of pingers 501, 503, 505 areneeded to locate badge 502 in a two dimensional space, as explainedabove in connection with FIGS. 11, 12, 13A. At least three pingers areneeded to locate badge 502 in three dimensional space as explained abovein connection with FIGS. 11, 13B, 13C.

For instance, badge 502 may include a lookup table that includes thelocation of each fixed pinger, such that badge 502 can determine a lociof possible locations for itself based on knowing the location of thepinger similar to the spheres and circles discussed in relation withFIGS. 13A and 13B. In another instance, the unique ID included in therespective excitation signal 574, 576, 578 provides information relatedto the location of the respective fixed pinger 501, 503, 505. In onecase, the unique ID is the location coordinates of the fixed pinger. Assuch, when badge 502 receives the respective excitation signal 574, 576,578, badge 502 knows the location of the respective pinger 501, 503, 505from the pinger ID and the distance badge 502 is from the respectivepinger 501, 503, 505 based on the time difference between the generationof the respective excitation signal 574, 576, 578 and the reception ofthe respective excitation signal 574, 576, 578. In another case, badge502 can use the signal strength of the respective excitation signals574, 576, 578. Based on the signal strength information, badge 502 maydetermine a loci of possible locations for itself.

Once badge 502 determines its location, badge 502 generates ID signal518 which is sent to receiver or transceiver 506. Receiver 506 forwardsthe location information on to central computing device 514. Sincereceiver 506 is not used in determining the location of badge 502,receiver 506 may be positioned at an arbitrary location and receive IDsignals 518 from various areas, such as area 512. In one embodiment,badge 502 sends an RF ID signal 518 and receiver 506 is located in ahallway adjacent several rooms in a hospital ward. Since RF signals canpenetrate walls, receiver 506 may receive signals from badges 502positioned in several rooms of the hospital ward.

In one embodiment wherein badge 502 determines its own distancemeasurements and hence location, excitation signals 574, 576, 578 frompingers 501, 503, 505, respectively, are RF signals and ID signal 518 isan RF signal. As stated above, an advantage of using RF technology isthat RF signals are not blocked by obstructions in a similar manner asline of sight systems (IR based). However, one of the disadvantages ofRF based systems is that RF signals are susceptible to interference,such as attenuation by objects, and multiple reflections. Theattenuation of excitation signals 574, 576, 578 or multiple reflectionsof excitation signals 574, 576, 578 may introduce errors into thecalculation of the location of badge 502. (Attenuation and multiplereflections effect calculations based on signal strength. Multiplereflections effect calculations based on timing information.)

Referring to FIG. 16, locating system 500 further includes a fixedlocation transceiver 580 positioned in area 512. Fixed transceiver 580knows its location relative to fixed pingers 501, 503, 505. Fixedtransceiver 580 is configured to receive excitation signals 574, 576,578 and to determine distance measurements to pingers 501, 503, 505 anda calculated location, shown illustratively as transceiver 581 in FIG.16. Transceiver 580 generates an ID signal 583 which is received bytransceiver 506 and includes at least an indication of the calculatedlocation 581 of transceiver 580.

As shown in FIG. 16 the calculated location 581 of transceiver 580 isdisplaced from the known location of transceiver 580 by a distance 582.The difference between the calculated location 581 and the true locationof transceiver 580 may be caused by interference or multiple reflectionsor both. However, by knowing the error distance 582 introduced in thelocation of transceiver 580, a better estimate of the location of badge502 may be made by central computing device 514. That is, the calculatedlocation of badge 502 may be offset by a distance corresponding todistance 582.

In one embodiment of locating system 500, the above enumerated examplesuse RF for transmitting both excitation signals if needed and IDsignals. Further, ultra-wideband technology (UWB) may be used to assistin minimizing the effects of interference and multiple reflections.

Another exemplary locating system is shown in FIGS. 17–19. Locatingsystem 700 includes one or more transceivers 706, 708, 710. Eachtransceiver 706, 708, 710 is configured to generate a signal which isdetectable by a badge 702 which is associated with an asset 704. In oneexample, the signal generated by transceivers 706, 708, 710 is anexcitation signal which causes badge 702 to generate an ID signalincluding a unique ID associated with asset 704.

Referring to FIG. 17, transceivers 706, 708, 710 are positioned within aroom 712. Transceivers 706, 708, 710 are configured to generate anexcitation signal in a specified direction based on the geometry of therespective transceiver, such as generally normal to the front of therespective transceiver. As shown in FIG. 17, transceiver 706 generatesan excitation signal generally in direction 716. The excitation signalgenerated by transceiver 706 is of limited extent in substantially onedimension. As illustratively shown in FIG. 17, the excitation signal isgenerally defined by a plane 717 that is generally normal to floor 721of area 712. As such, badge 702 receives the excitation signal generatedby transceiver 706 regardless of its altitude if badge 702 is positionedin plane 717 along direction 716 relative to transceiver 706.

If badge 702 is so positioned, then badge 702 acknowledges the receptionof the excitation signal by emitting an ID signal including the IDassociated with the badge 702. However, if badge 702 is not positionedrelative to transceiver 706 along direction 716, then badge 702 wouldnot receive the excitation signal from transceiver 706 and thereforewould not generate an ID signal. (It is understood that badge 702 mightgenerate an ID signal in response to being in line with one of the othertransceivers 708 and 710.)

Based on either the signal strength of at least one of the excitationsignal and the ID signal or the time delay between the generation of theexcitation signal and the reception of the ID signal from badge 702,transceiver 706 or computing device 714 is able to calculate the depthor distance from transceiver 706 to badge 702. Further, by knowing thedirection, such as direction 716, associated with the emission of theexcitation signal, transceiver 706 or computing device 714 is able todetermine a two-dimensional position of badge 702 in room 712.

In one variation, transceivers 706, 708, 710 are steerable, for example,about an axis such that the direction of the respective excitationsignal can be changed over time. As such, a two dimensional location,such as the position of badge 702 over floor 721 regardless of altitudeis roughly determined by sweeping a transceiver's excitation signalthrough room 712 and recording the direction corresponding to badge 702and the depth of badge 702 within room 712 based on the time betweengeneration of the excitation signal and the reception of the badge IDsignal or based on the signal strength of at least one of the excitationsignal and the ID signal. As shown in FIG. 17, transceiver 706 issweepable in directions 718, 720 about an axis 722. It should beappreciated that in this variation locating system 700 only requires asingle transceiver, such as transceiver 706, to determine a twodimensional location of badge 702 since a single transceiver can coverthe entire area 712 by sweeping through area 712 and since the depth ofbadge 702 can be determined by either signal strength or timinginformation. However, additional transceivers, such as transceivers 708,710, may be used to increase the accuracy of locating system 700.

In one example, transceivers 706, 708, 710 are mechanically steerable,such as by securing each transceiver 706, 708, 710 to a base (not shown)which is rotatable using a controller (not shown). In another example,transceivers 706, 708, 710 are steerable using MEMS technology, such asby electrically actuating a plurality of directional transmitters formedon a wafer of each transceiver 706, 708, 710. In yet another example,transceivers 706, 708, 710 are both mechanically and electronicallysteerable.

In another variation, the excitation signal generated by transceiver 706is of limited extent in two dimensions and the position of badge 702 inarea 712 is determined by sweeping at least one transceiver, such astransceiver 706, in multiple directions. Badge 702 will generate an IDsignal when it is generally positioned along a line defined by thedirection of the excitation signal as opposed to the plane defined bythe excitation signal in FIG. 17, since the excitation signal of thisvariation is of limited extent in two dimensions. As shown in FIG. 18,transceiver 706 is sweepable in directions 718, 720 about axis 722 andin directions 726, 728 about axis 730.

The direction of badge 702 relative to transceiver 706 is determined bysweeping transceiver 706 throughout room 712 and recording or otherwisedenoting the direction corresponding to badge 702. The depth of badge702 within room 712 is based on the time between generation of theexcitation signal and the reception of the badge ID signal or is basedon the signal strength of at least one of the excitation signal and theID signal. It should be appreciated that in this variation, locatingsystem 700 only requires a single transceiver, such as transceiver 706,to determine a three dimensional location of badge 702 since a singletransceiver can cover the entire area 712 by sweeping through area 712in multiple directions and since the depth of badge 702 can bedetermined by either signal strength or timing information. However,additional transceivers, such as transceivers 708, 710, may be used toincrease the accuracy of locating system 700.

In a further variation, transceivers 706, 708, 710 and/or centralcomputing device 714 do not rely on signal strength information ortiming information to determine either a two-dimensional location or athree-dimensional location of badge 702 in area 712. Referring to FIG.19, transceiver 706 is configured to be steerable in directions 718, 720about an axis 722 and transceiver 708 is configured to be steerable indirections 730, 732 about an axis 734. Further, both transceiver 706 andtransceiver 708 are configured to generate an excitation signal that isof limited extent in one dimension. As illustratively shown in FIG. 19,plane 717 generally defines the extent of the excitation signal oftransceiver 706 generally along a direction 716 and a plane 737generally defines the extent of the excitation signal of transceiver 708generally along a direction 736. Both planes 717, 737 are generallynormal to floor 721 of area 712.

If badge 702 is positioned relative to transceiver 706 within plane 717,then badge 702 acknowledges the excitation signal from transceiver 706by generating an ID signal. However, if badge 702 is not so positioned,then badge 702 would not receive the excitation signal from transceiver706 and therefore would not generate an ID signal. Similarly, if badge702 is positioned relative to transceiver 708 within the plane includingdirection 736, then badge 702 acknowledges the excitation signal fromtransceiver 708 by generating an ID signal. However, if badge 702 is notso positioned, then badge 702 would not receive the excitation signalfrom transceiver 708 and therefore would not generate an ID signal.

In one example, the excitation signals generated by transceivers 706,708 each include a transceiver ID which is unique to the respectivetransceiver. Further, the ID signal generated by badge 702 includes botha unique ID that is associated with asset 704 and the receivedtransceiver ID signal. As such, transceivers 706, 708 can determine towhich excitation signal badge 702 is responding.

In order to locate badge 702 in two dimensions, transceivers 706, 708sweep area 712 with their respective excitation signals until an IDsignal is generated by badge 702, indicating that badge 702 is alongeither direction 716 or 736. When transceiver 706 receives an ID signalcorresponding to its excitation signal, transceiver 706 records orotherwise denotes the direction corresponding to badge 702. Similarly,when transceiver 708 receives an ID signal corresponding to itsexcitation signal, transceiver 708 records or otherwise denotes thedirection corresponding to badge 702. As illustratively shown in FIG.19, badge 702 is positioned along direction 716 relative to transceiver706 and along direction 736 relative to transceiver 708. Based on aknowledge of the location of transceivers 706, 708 and the directions716, 736, central computing device 714 is able to apply knownmathematical techniques to determine that badge 702 is located somewherealong the intersection of planes 717, 737. Therefore, the location ofbadge 702 is somewhere along line 738.

In order to locate badge 702 in three dimensions, one of three methodsmay be used. First, at least one of transceivers 706, 708 may beconfigured to determine the depth of badge 702 relative to therespective transceiver, of transceivers 706, 708. The determined depthof badge 702 corresponds to two separate locations on line 738 creatingan ambiguity. In a first example, the ambiguity is removed becausetransceivers 706, 708 are generally located above potential locations ofbadge 702. In such a situation only a single transceiver is needed todetermine the depth of badge 702 because the single transceiver orcentral computing device 714 can eliminate any ambiguity by restrictingthe location of badge 702 to be lower than the respective transceiver orwithin area 712. In a second example, the ambiguity is removed becauseboth transceivers 706, 708 are configured to determine the depth ofbadge 702. The approximate location of badge 702 is then determinedbased on the depths calculated by both transceivers 706, 708.

Second, at least one of transceivers 706, 708 is configured to besteerable in multiple directions and to limit the extent of therespective excitation signal in two dimensions. As described above inconnection with FIG. 18, transceiver 706 may be configured to be issteerable in directions 718, 720 about axis 722 and in directions 726,728 about axis 730. As such, badge 702 may be located in threedimensions by steering transceivers 706, 708 in directions 718, 720 anddirections 730, 732, respectively. Once transceiver 706 receives an IDsignal from badge 702, transceiver 706 may limit the extent of therespective excitation signal in two dimensions and steer in directions726, 728 to determine an altitude of badge 702 along line 738.

Third, at least three transceivers, each steerable about at least oneaxis, are positioned in area 712, such as transceivers 706, 708, 710. Asdiscussed above transceivers 706, 708 are able to locate badge 702 intwo dimensions at the intersection of planes 717, 737. Transceiver 710is configured to be steerable in directions 740, 742 about an axis 744and to generate an excitation signal. A plane 747 generally defines theextent of the excitation signal of transceiver 710 generally along adirection 746. By knowing the direction 746 which corresponds to badge702 receiving the excitation signal from transceiver 710 andsubsequently generating an ID signal, the location of badge 702 alongline 738 may be narrowed to generally a point 746.

Another exemplary locating system is shown in FIGS. 20–21. Locatingsystem 800 includes one or more cameras 802, such as cameras 802 a and802 b which are positioned within an area of interest, such as a room812. Cameras 802 are configured to detect the presence of an indicator804 corresponding to an asset 806. Example indicators include the colorof clothing being worn by an individual, a badge or name plateassociated with an individual or equipment, a temperaturecharacteristic, such as a heat image associated with a person, etc.

In one example, indicator 804 is a badge or nameplate. Camera 802 isconfigured to detect the presence of badge 804 based on a characteristicof badge 804, such as color or emission. Known image processingtechniques can be implemented by camera 802 and/or central computingdevice 814 to detect the presence of badge 804. Further, camera 802 maybe configured to capture an image of the face of a person associatedwith a badge such that conventional image recognition techniques may beused to determine the identity of the person.

Camera 802 is further configured to adjust the focal length associatedwith camera 802 to bring badge 804 into focus. Badge 804 may includewriting or other markings that are viewable by camera 802. Based on thefocal length of camera 802, the depth or distance of badge 804 fromcamera 802 can be determined. For example, assuming the optics of camera802 may be represented as a thin-lens, the depth of badge 804 relativeto camera 802 may be approximately calculated by equation (5)

$\begin{matrix}{z_{1} = \frac{1}{\frac{1}{f} - \frac{1}{z_{2}}}} & (5)\end{matrix}$wherein z₁ is the depth of an object plane containing badge 804, f isthe focal length of camera 802 and z₂ is the distance to an image planeof camera 802 which is assumed to be a fixed value. As such, once badge804 is detected by camera 802, the depth of badge 804 can also becalculated.

In one example, the location of badge 804 in two dimensions may bedetermined from the depth calculations of two cameras 802 a, 802 bpositioned at an angle to each other. As shown in FIG. 20, cameras 802a, 802 b are generally at a right angle to each other. However, cameras802 a, 802 b may be placed at any angle relative to each other exceptfor 180°. As shown in FIG. 20, badge 804 is located within a field ofview 820 a of camera 802 a and within a plane 822 a a distance 824 afrom camera 802 a. Similarly, badge 804 is located within a field ofview 820 b of camera 802 b and within a plane 822 b a distance 824 bfrom camera 802 b. The location of badge 804 may be determined in twodimensions based on calculating an intersection 826 of object planes 824a, 824 b of cameras 802 a, 802 b, respectively.

In another example, a single camera such as camera 802 a may be used todetermine the location of badge 804 in two dimensions or in threedimensions. Referring to FIG. 21, an illustration of object plane 822 a(corresponding to the plane determined to contain badge 804 based on thefocal length of camera 802 a) of camera 802 a is shown. At this point,locating system based solely on camera 802 a knows the location of badge804 in one dimension, a depth from camera 802 a. The location of badge804 in a second and a third dimension may be determined by severalmethods.

In a first method, the location of badge 804 in at least either a seconddimension or in a second dimension and a third dimension may be based onthe location of badge 804 in object plane 822 a. As shown in FIG. 21,badge 804 is positioned to the left of a vertical centerline 828 ofobject plane 822 a and above a horizontal centerline 830 of object plane822 a. The horizontal position or dimension of badge 804 is determinedby calculating a horizontal offset percentage associated with badge 804.The offset percentage is calculated by dividing the horizontal offset ofbadge 804 from vertical centerline 828, as represented by the number ofpixels 832 by the total half field view number of pixels 834. The offsetpercentage is then multiplied by a known distance value for the halffield of view in the horizontal extent of camera 802 a to determine thedistance badge 804 is from vertical centerline 828 of camera 802 a. Assuch, by knowing the direction of camera 802 a, badge 804 may be locatedin two dimensions.

To locate badge 804 in three dimensions a vertical position or dimensionof badge 804 in object plane 822 a must be determined in addition to thehorizontal position or dimension of badge 804 and the depth of badge804. The vertical position or dimension of badge 804 is determined bycalculating a vertical offset percentage associated with badge 804. Thevertical offset percentage is calculated by dividing the vertical offsetof badge 804 from horizontal centerline 830, as represented by thenumber of pixels 836 by the total half field view number of pixels 838in the vertical extent of object plane 822 a. The vertical offsetpercentage is then multiplied by a known distance value for the halffield of view in the vertical extent of camera 802 a to determine thedistance badge 804 is from horizontal centerline 830 of camera 802 a. Assuch, by knowing the direction of camera 802 a, badge 804 may be locatedin three dimensions.

In a second method, the location of badge 804 in at least either asecond dimension or in a second dimension and a third dimension may bebased on the direction of camera 802 a corresponding to badge 804 beingcoincident with a centerline 828, 830 or center point 840 of objectplane 822 a. Camera 802 a is configured to be mechanically steerable inat least one direction. Referring to FIG. 21, in one example camera 802a is steerable in directions 848, 850 about an axis 852. To determine asecond dimension related to badge 804, camera 802 a is steered untilbadge 804 is aligned with vertical centerline 828 of object plane 822 a.Based on the direction of camera 802 a and the depth of badge 804, thelocation of badge 804 may be determined in two dimensions. In anotherexample, camera 802 a is steerable in directions 848, 850 about axis 852and is steerable in directions 842, 844 about an axis 846. Camera 802 ais steered about axes 846, 852 until badge 804 is generally aligned withcenter point 840 of object plane 822 a. Therefore, based on thedirection of camera 802 a and the depth of badge 804, the location ofbadge 804 may be determined in three dimensions.

In another embodiment, cameras 802 a and 802 b may be replaced with aplurality of scanning lasers mounted on one or more surfaces of room812, and badge 804 may be replaced with a tag or label including a barcode indicator that identifies the associated asset. In such anembodiment, the lasers are movably mounted to surfaces in room 812 andelectronically controlled to collectively scan the entire room 812 todetect and read the bar code using conventional bar code technology orother suitable techniques. In this manner, the asset associated with thebar code may be identified regardless of its location in room 812, solong as the bar code is within the line-of-sight of the scanning lasers.

In yet another embodiment, a plurality of lasers are arranged in fixedlocations around room 812. Each laser is configured to detectinterference caused by objects when objects pass through the beam of thelasers. The lasers may be situated at known angles relative to oneanother to permit two or three dimensional detection of objects. Forexample, a first plurality of laser may be located in a substantiallyhorizontal row along one wall of room 812, and a second plurality oflasers may be located in a substantially horizontal row along a secondwall of room 812 that is perpendicular to the first wall. When an assetpasses through the various beams of the lasers and causes detectableinterference, a computing device coupled to the lasers is configured todetermine which laser(s) detect the interference. Since the position ofeach laser is known, the computing device is able to determine a twodimensional location of the asset. It should be understood that thelasers may further be configured to sweep vertically to detectinterference caused by assets, regardless of the altitude of the asset.Additionally, a third plurality of lasers may be added, arranged in asubstantially vertical column on one wall of room 812 and configured tosweep horizontally, to determine the altitude of the asset according toprinciples described above, and provide a three-dimensional location ofthe asset. Moreover, any of the identification techniques describedherein may be used with this variation of the invention to identify theasset in addition to determining its location.

Another exemplary locating system is shown in FIG. 22. Referring to FIG.22, a facility 900, such as a healthcare facility, includes a pluralityof areas, such as patient rooms 902 a–e, waiting room 904, nurse station906, and break room 908, all connected by a hallway 910. Facility 900includes a locating system 920 including a plurality of transmitterspositioned throughout facility 900, such as transmitters 922 a–j, atleast one badge 924 associated with an asset 926, a receiver 928, and acentral computing device 930.

Transmitters 922 a–j are configured to generate an ID signal (not shown)containing a unique ID associated with the respective transmitter 922a–j. The transmitter ID may be set by the setting of a conventional dipswitch associated with each of transmitters 922 a–j. In one example,transmitters 922 a–j include one of an IR transmitter, an ultrasoundtransmitter, or other line-of-sight transmitter. In another example,transmitters 922 a–j include a low-frequency RF transmitter.Transmitters 922 a–j, in one example, include a battery (not shown) toprovide power to generate the respective ID signal. In another example,transmitters 922 a–j are coupled to a power supply (not shown) such as afacility electrical system.

Badge 924 is configured to receive the ID signal generated bytransmitters 922 a–j when badge 924 is proximate to one of transmitters922 a–j. Referring to FIG. 22, badge 924 receives the ID signalgenerated by transmitter 922 e because badge 924 is located in patientroom 902 e. Badge 924 is generally similar to badge 12 and is configuredto generate an ID signal associated with badge 924. The badge ID signalincludes an ID unique to badge 924 (asset 926) and at least the lastreceived transmitter ID from one of transmitters 922 a–j. In oneexample, badge 924 generates an ID signal every time badge 924 receivesa new transmitter ID, such as when badge 924 leaves patient room 902 eand enters hallway 910 proximate to transmitter 922 j. In anotherexample, badge 924 generates a badge ID signal at a predeterminedinterval and includes all transmitter IDs received since the previouslytransmitted badge ID signal. In yet another example, badge 924 transmitsthe badge ID signal at two or more predetermined time intervals based ona characteristic of a displacement sensor (not shown) associated withbadge 924. In the above examples, badge 924 is configured to store oneor more transmitter IDs for later transmission in a badge ID signal.

Badge 924 includes an RF transmitter or other transmitter that iscapable of sending the badge ID signal to receiver 928 which may becentrally located in facility 900. As such, the transmitter associatedwith badge 924 must be capable of penetrating facility walls and otherobstructions. Receiver 928 is connected to central computing device 930through either a wired or wireless connection, represented in FIG. 22 as932.

The location of transmitters 922 a–j are stored in or otherwise madeavailable to central computing device 930. As such, the location ofbadge 924 is determined by correlating the transmitter ID(s) transmittedwith the badge ID signal with the known locations of transmitters 922a–j. Central computing device 930 stores the location informationrelated to badge 924 for later processing or retrieval.

Referring to FIG. 23, patient room 902 e is shown with transmitter 922 eand additional transmitters 922 k–n. Transmitters 922 k–n, liketransmitter 922 e, generate a transmitter ID signal which is received bybadge 924. However, transmitters 922 k–n generate their respectivetransmitter IDs in limited areas, 934 a–d respectively, of patient room902 e. As such, badge 924 only receives an ID signal from transmitters922 k–n if badge 924 is within a respective area of one of transmitters922 k–n. For example, as shown in FIG. 23, badge 924 will receive an IDsignal from transmitter 922 m, but not from transmitters 922 k,l,n. Assuch, locating system 900 not only knows that badge 924 is in patientroom 902 e, due to transmitter 922 e or 922 m, but also that badge 924is in region 934 c of patient room 902 e corresponding to transmitter922 m. Therefore transmitters 922 k–n increase the resolution oflocating system 900 over transmitters 922 a–j. It should be understoodthat transmitter 922 e is optional in light of transmitters 922 k–n.

Regions 934 a–d are shown in FIG. 23 to be mutually exclusive regions.However, it is within the scope of the present invention that one ormore of regions 934 a–d may overlap one or more of the other regions 934a–d. As such, badge 924 at a given location may receive a transmitter IDsignal from one or more of transmitters 922 k–n. When badge 924 receivesa transmitter ID signal from more than one of transmitters 922 k–n, thetechniques for determining the location of badge 924 relative to themultiple transmitters of transmitters 922 k–n based on at least one ofsignal strength and timing information may be implemented in locatingsystem 900.

In one example, transmitters 922 k–n are RF transmitters which generatetheir respective ID signals at a low frequency, such as about 125 KHz.In one case transmitters 922 k–n are mounted to a ceiling of patientroom 902 e and generate their respective ID signals in a region aboutsix feet below the ceiling and in about a three foot radius of therespective transmitter 922 k–n. In one example, badge 924 includes an RFtransmitter which is capable of sending a badge ID signal to receiver928 over a distance of about 200 to 300 feet.

One feature of locating system 900 is that a network connectingtransmitters, receivers, or transceivers in every location of facility900 is not required. This may reduce the cost associated withimplementing locating system 900 into an existing facility.

It should be understood that various signals other than conventionalelectronic signals may be used to locate and track assets consistentwith the teachings of the various embodiments of the invention describedabove. For example, badges may be configured to maintain a particulartemperature or temperature characteristic which, when detected bysensors permits location of the asset associated with the badge.Conventional thermal imaging technology may be employed to identifycertain distinguishing characteristics of badges, thereby permittingidentification of the asset associated therewith. Additionally, thebadge may be configured to maintain a temperature corresponding to theasset such that the locating and tracking system can also determine thetemperature of the tracked asset. Such temperature information may beused to trigger activities. For example, if a sink is a tagged asset, analarm may be activated if the sink temperature exceeds a predeterminedthreshold.

The location information collected and processed by any of the abovementioned location systems 10, 500, 700, 800, 900 can be used inapplications designed to improve the level of care provided to patientsin a hospital, reduce the demands on hospital staff, and/or maximize theefficiency of the healthcare environment. For instance, as explainedabove in connection with ABT 10, the collected location information canbe used to determine handwashing compliance, to easily locate assets, todetermine waste handling compliance, to associate assets with particularpatients, to provide data for healthcare environment simulations, andmany more applications. Additionally, many of the locating and trackingtechniques described herein may be employed to track assets, such aslaboratory test results, through pneumatic systems. In such anapplication, the locating and tracking system may determine, forexample, exactly where in the tubing network of the pneumatic system aparticular asset (e.g., specimens or results of a particular patient)are located (or lodged).

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and description isto be considered as exemplary and not restrictive in character, it beingunderstood that only exemplary embodiments have been shown and describedand that all changes and modifications that come within the spirit ofthe invention and the attached claims are desired to be protected.

1. A system for tracking a plurality of movable assets in a healthcareenvironment, the system comprising: a plurality of badges, each badge ofthe plurality of badges including a transmitter, the badge being adaptedto be coupled to an asset, and the badge being configured to transmit anidentification signal identifying the badge; and a locating systemconfigured to receive the identification signal from the respectivebadge and to determine a location of the asset in the healthcareenvironment including a height associated with the asset based at leastin part on the identification signal, the locating system being furtherconfigured to determine if the height of the asset is an expectedheight.
 2. The system of claim 1, wherein the expected height of theasset is assigned based on the type of asset.
 3. The system of claim 1,wherein a first asset is a patient and the expected height of thepatient corresponds to a height above a threshold height from the floor.4. The system of claim 3, wherein the threshold height is at least threefeet above the floor.
 5. The system of claim 3, wherein the locatingsystem is further configured to perform at least one of the following ifthe first asset is at an unexpected height, send an indication to acaregiver and initiate an alarm.
 6. The system of claim 5, wherein thelocating system is configured to wait a predetermined time period todetermine if the first asset has moved to an expected height beforeperforming at least one of the following, send an indication to acaregiver and initiate an alarm.
 7. The system of claim 3, wherein thelocating system is further configured to receive equipment statusinformation from a sensor associated with a first piece of equipmentpositioned in the healthcare environment.
 8. The system of claim 7,wherein the locating system determines if the first asset is at anunexpected height based on the location of the first asset and a statusof the first piece of equipment.
 9. The system of claim 8, wherein thefirst piece of equipment is a bed and the sensor provides statusinformation of the position of a siderail.
 10. The system of claim 9,wherein the locating system determines that the first asset is at anunexpected height if the first asset is at a height below the thresholdheight and the sensor indicates that the siderail is in a down position.11. The system of claim 8, wherein the first piece of equipment is a bedand the sensor provides status information on the configuration of thebed.
 12. The system of claim 11, wherein the locating system determinesthat the first asset is at an expected height if the first asset is at aheight below the threshold height and the sensor indicates that the bedis in a low configuration.
 13. The system of claim 3, wherein the badgeassociated with the first asset includes a displacement sensor andwherein the location system is further configured to use accelerationinformation provided by the displacement sensor to determine if thefirst asset is at an unexpected height.
 14. The system of claim 1,wherein the locating system includes means for receiving theidentification signal from each badge and means for determining thelocation of the corresponding asset.
 15. The system of claim 1, whereina second asset is a piece of equipment and the expected height of thepiece of equipment corresponds to a height above a threshold height fromthe floor.
 16. The system of claim 15, wherein the threshold height isat least three feet above the floor.
 17. The system of claim 15, whereinthe locating system is further configured to indicate that the secondasset is at an unexpected height.
 18. The system of claim 17, whereinthe locating system is configured to wait a predetermined time period todetermine if the second asset has moved to an expected height.
 19. Thesystem of claim 15, wherein the badge associated with the second assetincludes a displacement sensor and wherein the location system isfurther configured to use acceleration information provided by thedisplacement sensor to determine if the second asset has changed itsheight.
 20. The system of claim 1, wherein a second asset is a piece ofequipment and the expected height of the piece of equipment correspondsto a range of heights.
 21. The system of claim 1, wherein the locatingsystem prevents the movement of a first asset based on the location ofat least a second asset.
 22. The system of claim 1, wherein the locatingsystem includes a plurality of receivers positioned throughout thehealthcare environment, each of the receivers configured to receive anidentification signal from a badge positioned within range of thereceiver, and a processor configured to receive from the plurality ofreceivers the identification of the badges detected by each receiver,the processor being configured to determine the location of each assetbased on the locations of the receivers which detected the badgeassociated with the asset.
 23. A system for tracking a plurality ofmovable assets in a healthcare facility, the system comprising: aplurality of badges, each badge of the plurality of badges including atransmitter, the badge being adapted to be coupled to an asset, and thebadge being configured to transmit an identification signal identifyingthe badge, a first badge being associated with a first movable asset; alocating system configured to receive the identification signal from thefirst badge and to determine a location of the first movable asset inthe healthcare facility based at least in part on the identificationsignal received from the first badge; and at least one portable device,the portable device including a controller, a display, a memory, aninput device, and a transceiver, the portable device being configured togenerate a request signal to be received by the locating systemrequesting the location of the first movable asset in the healthcarefacility, to receive a location signal from the locating systemindicating the location of the first movable asset and to provideappropriate directions to a first location in the healthcare facilitybased on the location of the first movable asset.
 24. The system ofclaim 23, wherein the first location corresponds to the location of thefirst movable asset.
 25. The system of claim 23, wherein the firstlocation corresponds to a location different than the identifiedlocation of the first movable asset.
 26. The system of claim 23, whereina user is associated with the portable device and the portable device isconfigured to provide appropriate directions based on the locationswithin a healthcare facility to which the user of the portable devicehas access.
 27. The system of claim 26, wherein the first locationcorresponds to a location within the facility different than thelocation of the first movable asset when the first movable asset is in alocation within the facility to which the user of the portable devicedoes not have access.
 28. The system of claim 27, wherein the firstmovable asset is a patient whose current location is in surgery and thefirst location is a waiting room associated with the surgery location ofthe patient.
 29. The system of claim 27, wherein the first movable assetis a piece of equipment whose current location is in an equipment roomand the first location corresponds to the location of a clerk associatedwith the equipment room.
 30. The system of claim 27, wherein theportable device is configured to allow the user to add the first assetto a watch list and to notify the user when the first asset is in alocation to which the user has access.
 31. The system of claim 23,wherein the appropriate directions are visual directions and aredisplayed on the display, the visual directions includes a map of thefacility including the location of the portable device, the location ofthe requested first movable asset, and a suggested route to the asset.32. The system of claim 31 wherein the suggested route corresponds toone of the shortest distance route to the first movable asset and theshortest time route to the first movable asset.
 33. The system of claim32, wherein the shortest time route is determined based at least in parton potential congestion in various locations along at least two routes.34. The system of claim 33, wherein the potential congestion in variouslocations along at least two routes is determined by an activitymonitoring system.
 35. The system of claim 34, wherein the activitymonitoring system accumulates the data from the plurality of badges,associates portions of the data with particular activities, andgenerates statistical analyses of the data associated with theparticular activities to identify characteristics associated with theparticular activities.
 36. The system of claim 31, wherein the map is athree dimensional map.
 37. The system of claim 36, wherein the mapincludes representations of various assets based on their currentlocations.
 38. The system of claim 23, wherein the appropriatedirections are visual instructions, the visual instructions including adirection-indicating symbol.
 39. The system of claim 23, wherein thefirst portable device includes a speaker and the appropriate directionsare audio directions.
 40. The system of claim 23, wherein the userrequests a second asset with the input device and the locating systemdetermines the location of the second asset and issues a command for thesecond asset to be taken to a second location.
 41. The system of claim40, wherein the second location is the current location of the user ofthe portable device.
 42. The system of claim 40, wherein the secondlocation is a location specified by the user of the portable device. 43.The system of claim 40, wherein the locating system determines if theasset is available based on information supplied by an activitymonitoring system.
 44. The system of claim 40, wherein an orderly isnotified of the request for the asset by the locating system.
 45. Thesystem of claim 23, wherein the user of the portable device is presentedwith a virtual facility including representations of various assets eachhaving a badge associated therewith, the representations beingpositioned within the virtual facility based on the location informationfor each asset.
 46. The system of claim 45, wherein a third asset hasmultiple representations, each representation selected for inclusion inthe virtual facility based on a status of the third asset.
 47. Thesystem of claim 46, wherein the third asset is a bed having a firstrepresentation corresponding to a bed having a raised head section. 48.The system of claim 45, wherein a representation of a fourth asset isanimated to simulate movement or use of the asset.
 49. The system ofclaim 48, wherein the fourth asset is an I/V pump and the animationrepresents that the pump is receiving power and is pumping.
 50. Thesystem of claim 45, wherein the user can select an asset within thevirtual facility to retrieve information related to the asset.
 51. Thesystem of claim 50, wherein the information is selected from the groupof maintenance records, specifications, status, and prior locations. 52.The system of claim 50, wherein the information is related to an alarmstatus associated with the asset.
 53. The system of claim 50, whereinthe user can remotely change the status of the asset.
 54. The system ofclaim 50, wherein the user can remotely change the configuration of theasset.
 55. The system of claim 45, wherein the various assets arecolor-coded based on a status of the respective asset.
 56. The system ofclaim 55, wherein a fifth asset is a caregiver and the caregiver iscolor-coded to indicate a contaminated status.
 57. The system of claim56, wherein the fifth asset is the user of the portable device.
 58. Asystem for tracking a plurality of movable assets in a healthcarefacility, the system comprising: a plurality of badges, each badge ofthe plurality of badges including a transmitter, the badge being adaptedto be coupled to an asset, and the badge being configured to transmit anidentification signal identifying the badge, a first badge beingassociated with a first movable asset; a locating system configured toreceive the identification signal from the first badge and to determinea location of the first movable asset in the healthcare facility basedat least in part on the identification signal received from the firstbadge; and a virtual facility interface including a display and an inputdevice, wherein the virtual facility interface presents a virtualfacility including a map of the facility and representations of variousassets each having a badge associated therewith, the representationsbeing positioned within the virtual facility based on the locationinformation determined by the locating system for each asset, at leastthe first asset including multiple representations including a firstrepresentation corresponding to a first status and a secondrepresentation corresponding to a second status.
 59. The system of claim58, wherein the virtual facility interface is a portable device carriedby a caregiver.
 60. The system of claim 58, wherein the user ispresented a three-dimensional representation of the facility.
 61. Thesystem of claim 58, wherein the first representation of the first assetis selected for inclusion in the virtual facility based on the firstasset having the first status, the status of the first asset beingdetermined by an activity monitoring system.
 62. The system of claim 58,wherein the first asset is a bed and the first representationcorresponds to a bed having a raised head section.
 63. The system ofclaim 58, wherein a representation of a second asset is animated tosimulate movement or use of the asset.
 64. The system of claim 63,wherein the second asset is an I/V pump and the animation representsthat the pump is receiving power and is pumping.
 65. The system of claim58, wherein the user can select an asset within the virtual facility toretrieve information related to the asset.
 66. The system of claim 65,wherein the information is selected from the group of maintenancerecords, specifications, status, and prior locations.
 67. The system ofclaim 65, wherein the information is related to an alarm statusassociated with the asset.
 68. The system of claim 58, wherein the usercan remotely change the status of the asset.
 69. The system of claim 58,wherein the user can remotely change the configuration of the asset. 70.The system of claim 58, wherein at least one of the various assets arecolor-coded based on a status of the respective asset.
 71. The system ofclaim 70, wherein a third asset is a caregiver and the caregiver iscolor-coded to indicate a contaminated status.
 72. The system of claim71, wherein the virtual facility interface is a portable device carriedby a first caregiver and the third asset is the first caregiverassociated with the portable device.
 73. The system of claim 58, whereinthe first badge determines the location of the first badge in thehealthcare facility based on transmitter identifying signals received bythe first badge.
 74. The system of claim 73, wherein the first badgedetermines the location of the first badge based in part on the signalstrength of the transmitter identifying signals received by the firstbadge.
 75. The system of claim 73, wherein the transmitter identifyingsignals each includes a timestamp identifying when the transmitteridentifying signal was sent and wherein the first badge determines thelocation of the first badge based in part on the timestamp of thetransmitter identifying signals received by the first badge.
 76. Thesystem of claim 58, wherein a processor determines the location of thefirst badge in the healthcare facility based on transmitter identifyingsignals received by the first badge.
 77. The system of claim 76, whereinthe processor determines the location of the first badge based in parton the signal strength of the transmitter identifying signals receivedby the first badge.
 78. The system of claim 76, wherein the transmitteridentifying signals each includes a timestamp identifying when thetransmitter identifying signal was sent and wherein the processordetermines the location of the first badge based in part on thetimestamp of the transmitter identifying signals received by the firstbadge.
 79. The system of claim 58, wherein a displacement sensorprovides a vertical acceleration measurement which is used by one of thefirst badge and a processor to determine if the corresponding asset hasfallen or has been dropped.